From 2440f23829a1180e293a08180003f1ffe6104fbe Mon Sep 17 00:00:00 2001
From: iko <ilyakooo0@gmail.com>
Date: Mon, 21 Jun 2021 20:52:48 +0300
Subject: [PATCH] Added non-breaking changes to reports (#82)

* bumped resolver

* Added non-breaking changes to report

* Removed dead file

* Added backward issue descriptions

* Issue description reversing

* Changed wording slightly
---
 app/Main.hs                                   |  39 +++--
 openapi-diff.cabal                            |   4 +-
 src/OpenAPI/Checker/Behavior.hs               |  20 ++-
 src/OpenAPI/Checker/Report.hs                 | 145 ++++++++++++------
 src/OpenAPI/Checker/Run.hs                    |  30 ++++
 src/OpenAPI/Checker/Subtree/Deriving.hs       |   6 -
 src/OpenAPI/Checker/Validate/Header.hs        |   8 +-
 src/OpenAPI/Checker/Validate/Link.hs          |   2 +-
 .../Checker/Validate/MediaTypeObject.hs       |  20 ++-
 src/OpenAPI/Checker/Validate/OAuth2Flows.hs   |  48 +++---
 src/OpenAPI/Checker/Validate/Operation.hs     |  11 +-
 src/OpenAPI/Checker/Validate/Param.hs         |  16 +-
 src/OpenAPI/Checker/Validate/RequestBody.hs   |   8 +-
 src/OpenAPI/Checker/Validate/Responses.hs     |   8 +-
 src/OpenAPI/Checker/Validate/Schema.hs        |  86 +++++++----
 src/OpenAPI/Checker/Validate/Server.hs        |  13 +-
 stack.yaml                                    |   2 +-
 stack.yaml.lock                               |   8 +-
 test/Spec.hs                                  |   2 +-
 test/Spec/Golden/TraceTree.hs                 |  19 +--
 test/golden/common/enum-anyof/report.md       |   6 +-
 test/golden/common/enum-anyof/trace-tree.yaml |   3 +-
 test/golden/common/id/report.md               |   6 +-
 test/golden/common/id/trace-tree.yaml         |   3 +-
 test/golden/common/json/recursive/report.md   |   6 +-
 .../common/json/recursive/trace-tree.yaml     |   3 +-
 test/golden/common/maximum-lowered/report.md  |  18 ++-
 .../common/maximum-lowered/trace-tree.yaml    |  10 +-
 .../allowEmptyValue/reset/report.md           |   8 +-
 .../allowEmptyValue/reset/trace-tree.yaml     |   3 +-
 .../parameters/allowEmptyValue/set/report.md  |  14 +-
 .../allowEmptyValue/set/trace-tree.yaml       |   6 +-
 .../operation/parameters/change/report.md     |  18 ++-
 .../parameters/change/trace-tree.yaml         |   8 +-
 .../parameters/required/false/add/report.md   |   6 +-
 .../required/false/add/trace-tree.yaml        |   3 +-
 .../parameters/required/false/del/report.md   |   6 +-
 .../required/false/del/trace-tree.yaml        |   3 +-
 .../parameters/required/reset/report.md       |  14 +-
 .../parameters/required/reset/trace-tree.yaml |   6 +-
 .../parameters/required/set/report.md         |   6 +-
 .../parameters/required/set/trace-tree.yaml   |   3 +-
 .../parameters/required/true/add/report.md    |   6 +-
 .../required/true/add/trace-tree.yaml         |   3 +-
 .../parameters/required/true/del/report.md    |  12 +-
 .../required/true/del/trace-tree.yaml         |   5 +-
 .../requestBody/mediaTypeObject/add/report.md |  14 +-
 .../mediaTypeObject/add/trace-tree.yaml       |   6 +-
 .../mediaTypeObject/change/report.md          |  18 ++-
 .../mediaTypeObject/change/trace-tree.yaml    |   9 +-
 .../requestBody/mediaTypeObject/del/report.md |   6 +-
 .../mediaTypeObject/del/trace-tree.yaml       |   3 +-
 .../requestBody/required/reset/report.md      |  14 +-
 .../required/reset/trace-tree.yaml            |   6 +-
 .../requestBody/required/set/report.md        |   6 +-
 .../requestBody/required/set/trace-tree.yaml  |   3 +-
 .../operation/responses/add/report.md         |   6 +-
 .../operation/responses/add/trace-tree.yaml   |   3 +-
 .../change/headers/mandatory/add/report.md    |  14 +-
 .../headers/mandatory/add/trace-tree.yaml     |   6 +-
 .../change/headers/mandatory/del/report.md    |   8 +-
 .../headers/mandatory/del/trace-tree.yaml     |   3 +-
 .../change/headers/optional/add/report.md     |   6 +-
 .../headers/optional/add/trace-tree.yaml      |   3 +-
 .../change/headers/optional/del/report.md     |   6 +-
 .../headers/optional/del/trace-tree.yaml      |   3 +-
 .../change/mediaTypeObject/add/report.md      |   6 +-
 .../mediaTypeObject/add/trace-tree.yaml       |   3 +-
 .../change/mediaTypeObject/change/report.md   |  18 ++-
 .../mediaTypeObject/change/trace-tree.yaml    |   9 +-
 .../change/mediaTypeObject/del/report.md      |  14 +-
 .../mediaTypeObject/del/trace-tree.yaml       |   6 +-
 .../operation/responses/del/report.md         |  12 +-
 .../operation/responses/del/trace-tree.yaml   |   5 +-
 .../common/property-removed-additional/a.yaml |  32 ++++
 .../common/property-removed-additional/b.yaml |  29 ++++
 .../property-removed-additional/report.md     |  25 +++
 .../trace-tree.yaml                           |  14 ++
 test/golden/common/property-removed/report.md |  28 +++-
 .../common/property-removed/trace-tree.yaml   |  13 +-
 .../golden/common/property-required/report.md |  18 ++-
 .../common/property-required/trace-tree.yaml  |   9 +-
 test/golden/common/recursive/report.md        |  20 ++-
 test/golden/common/recursive/trace-tree.yaml  |  15 +-
 test/golden/common/security-scheme/report.md  |  16 +-
 .../common/security-scheme/trace-tree.yaml    |   7 +-
 test/golden/common/servers/report.md          |  14 +-
 test/golden/common/servers/trace-tree.yaml    |   7 +-
 .../common/unguarded-recursive/report.md      |   8 +-
 .../unguarded-recursive/trace-tree.yaml       |   8 +-
 90 files changed, 872 insertions(+), 287 deletions(-)
 create mode 100644 src/OpenAPI/Checker/Run.hs
 delete mode 100644 src/OpenAPI/Checker/Subtree/Deriving.hs
 create mode 100644 test/golden/common/property-removed-additional/a.yaml
 create mode 100644 test/golden/common/property-removed-additional/b.yaml
 create mode 100644 test/golden/common/property-removed-additional/report.md
 create mode 100644 test/golden/common/property-removed-additional/trace-tree.yaml

diff --git a/app/Main.hs b/app/Main.hs
index 78e76cd..725b760 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -5,19 +5,14 @@ import Control.Monad.Except
 import Data.Aeson
 import qualified Data.ByteString.Lazy as BSL
 import Data.Default
-import Data.HList
 import qualified Data.Text.IO as T
 import qualified Data.Yaml as Yaml
 import FormatHeuristic
-import OpenAPI.Checker.Behavior
 import OpenAPI.Checker.Options
-import OpenAPI.Checker.Paths
-import OpenAPI.Checker.PathsPrefixTree
-import OpenAPI.Checker.Report
-import OpenAPI.Checker.Subtree
+import OpenAPI.Checker.Run
 import System.Exit
 import System.IO
-import Text.Pandoc
+import Text.Pandoc hiding (report)
 
 main :: IO ()
 main = do
@@ -33,23 +28,27 @@ main = do
                 fail "Exiting"
               Right s -> pure s
           Right s -> pure s
-  a <- traced (step ClientSchema) <$> parseSchema (clientFile opts)
-  b <- traced (step ServerSchema) <$> parseSchema (serverFile opts)
-  let result = runCompatFormula $ checkCompatibility HNil Root (ProdCons a b)
-      runPandocIO :: PandocIO a -> ExceptT Errors IO a
+  a <- parseSchema (clientFile opts)
+  b <- parseSchema (serverFile opts)
+  let runPandocIO :: PandocIO a -> ExceptT Errors IO a
       runPandocIO x = lift (runIO x) >>= either (throwError . DocumentError) pure
       options = def {writerExtensions = githubMarkdownExtensions}
-      output :: Either (PathsPrefixTree Behave AnIssue 'APILevel) () -> ExceptT Errors IO ()
-      output = case outputMode opts of
-        StdoutMode -> lift . T.putStrLn <=< runPandocIO . writeMarkdown options . generateReport
+      write :: Pandoc -> ExceptT Errors IO ()
+      write = case outputMode opts of
+        StdoutMode -> lift . T.putStrLn <=< runPandocIO . writeMarkdown options
         FileMode f -> case formatFromFilePath f of
           Nothing -> \_ -> throwError UnknownOutputFormat
-          Just (TextWriter writer) -> lift . T.writeFile f <=< runPandocIO . writer options . generateReport
-          Just (ByteStringWriter writer) -> lift . BSL.writeFile f <=< runPandocIO . writer options . generateReport
-  either handler pure <=< runExceptT $ output result
-  case result of
-    Right () -> exitSuccess
-    Left _ -> exitWith $ ExitFailure 1
+          Just (TextWriter writer) -> lift . T.writeFile f <=< runPandocIO . writer options
+          Just (ByteStringWriter writer) -> lift . BSL.writeFile f <=< runPandocIO . writer options
+      -- output :: Either (PathsPrefixTree Behave AnIssue 'APILevel) () -> ExceptT Errors IO ()
+      -- output inp = do
+      --   undefined
+      (report, status) = runReport (a, b)
+  either handler pure <=< runExceptT $ write report
+  case status of
+    NoBreakingChanges -> exitSuccess
+    BreakingChanges -> exitWith $ ExitFailure 1
+    OnlyUnsupportedChanges -> exitWith $ ExitFailure 2
 
 data Errors
   = DocumentError PandocError
diff --git a/openapi-diff.cabal b/openapi-diff.cabal
index 34302f9..fdcbbe5 100644
--- a/openapi-diff.cabal
+++ b/openapi-diff.cabal
@@ -35,7 +35,7 @@ common common-options
     -Wno-missing-local-signatures
     -Wno-unsafe
   default-language:    Haskell2010
-  build-depends:       base >= 4.12.0.0 && < 4.15
+  build-depends:       base >= 4.12.0.0 && < 4.16
                      , bytestring
                      , text
 
@@ -104,6 +104,7 @@ library
                      , transformers
                      , mtl
                      , aeson
+                     , generic-data
   hs-source-dirs:      src
   exposed-modules:  Data.HList
                   , OpenAPI.Checker.Behavior
@@ -134,6 +135,7 @@ library
                   , OpenAPI.Checker.Report
                   , Data.OpenUnion.Extra
                   , OpenAPI.Checker.Report.Jet
+                  , OpenAPI.Checker.Run
 
 executable openapi-diff
   import:              common-options
diff --git a/src/OpenAPI/Checker/Behavior.hs b/src/OpenAPI/Checker/Behavior.hs
index 5d2f783..5e3ecd6 100644
--- a/src/OpenAPI/Checker/Behavior.hs
+++ b/src/OpenAPI/Checker/Behavior.hs
@@ -2,6 +2,8 @@ module OpenAPI.Checker.Behavior
   ( BehaviorLevel (..)
   , Behavable (..)
   , Issuable (..)
+  , Orientation (..)
+  , toggleOrientation
   , Behavior
   , AnIssue (..)
   )
@@ -43,9 +45,25 @@ type instance AdditionalQuiverConstraints Behave a b = Behavable a b
 
 class (Typeable l, Ord (Issue l), Show (Issue l)) => Issuable (l :: BehaviorLevel) where
   data Issue l :: Type
-  describeIssue :: Issue l -> Blocks
+
+  -- | The same issues can be rendered in multiple places and might
+  -- require different ways of represnting them to the user.
+  --
+  -- In practice each issue requires a maximum of two different representations:
+  -- based on the context the issue might need to be rendered as "opposite" ('Backward')
+  -- – for example when rendering non-breaking changes everything should be
+  -- reversed (a consequence of the way we generate non-breaking changes).
+  describeIssue :: Orientation -> Issue l -> Blocks
+
   issueIsUnsupported :: Issue l -> Bool
 
+data Orientation = Forward | Backward
+  deriving stock (Eq, Ord)
+
+toggleOrientation :: Orientation -> Orientation
+toggleOrientation Forward = Backward
+toggleOrientation Backward = Forward
+
 -- | A set of interactions having common unifying features
 type Behavior = Paths Behave 'APILevel
 
diff --git a/src/OpenAPI/Checker/Report.hs b/src/OpenAPI/Checker/Report.hs
index dc1f80d..d77a5e6 100644
--- a/src/OpenAPI/Checker/Report.hs
+++ b/src/OpenAPI/Checker/Report.hs
@@ -1,15 +1,20 @@
 module OpenAPI.Checker.Report
   ( generateReport
+  , ReportInput (..)
+  , ReportStatus (..)
+  , Pandoc
   )
 where
 
 import Control.Monad.Free hiding (unfoldM)
 import Control.Monad.Reader
 import Control.Monad.Writer
+import Data.Aeson (ToJSON)
 import Data.Either
 import Data.Foldable
 import Data.Function
 import Data.Functor
+import Data.Functor.Const
 import Data.List.NonEmpty
 import qualified Data.List.NonEmpty as NE
 import qualified Data.Map as M
@@ -22,6 +27,7 @@ import Data.Text (Text)
 import qualified Data.Text as T
 import Data.TypeRepMap hiding (empty)
 import Data.Typeable
+import Generic.Data
 import OpenAPI.Checker.Behavior
 import OpenAPI.Checker.Paths
 import OpenAPI.Checker.PathsPrefixTree hiding (empty)
@@ -31,27 +37,79 @@ import OpenAPI.Checker.Validate.OpenApi
 import OpenAPI.Checker.Validate.Schema
 import Text.Pandoc.Builder
 
-generateReport :: Either (P.PathsPrefixTree Behave AnIssue 'APILevel) () -> Pandoc
-generateReport (Right ()) = doc $ header 1 "No breaking changes found ✨"
-generateReport (Left errs) = doc $
-  runReportMonad jets $ do
-    let (unsupported, breaking) = P.partition (\(AnIssue i) -> issueIsUnsupported i) errs
-        breakingChangesPresent = not $ P.null breaking
-        unsupportedChangesPresent = not $ P.null unsupported
-    smartHeader "Summary"
-    tell $
-      simpleTable
-        (para
-           <$> [ refOpt breakingChangesPresent breakingChangesId "⚠️ Breaking changes"
-               , refOpt unsupportedChangesPresent unsupportedChangesId "🤷 Unsupported feature changes"
-               ])
-        [para . show' <$> [P.size breaking, P.size unsupported]]
-    when breakingChangesPresent $ do
-      smartHeader $ anchor breakingChangesId <> "⚠️ Breaking changes"
-      incrementHeaders $ showErrs breaking
-    when unsupportedChangesPresent $ do
-      smartHeader $ anchor unsupportedChangesId <> "🤷 Unsupported feature changes"
-      incrementHeaders $ showErrs unsupported
+type Changes = P.PathsPrefixTree Behave AnIssue 'APILevel
+
+type ProcessedChanges a = P.PathsPrefixTree Behave (FunctorTuple (Const Orientation) AnIssue) a
+
+data FunctorTuple f g a = FunctorTuple (f a) (g a)
+  deriving stock (Eq, Ord)
+
+data ReportInput = ReportInput
+  { breakingChanges :: Changes
+  , nonBreakingChanges :: Changes
+  }
+  deriving stock (Generic)
+  deriving (Semigroup, Monoid) via (Generically ReportInput)
+  deriving anyclass (ToJSON)
+
+data ReportStatus
+  = BreakingChanges
+  | NoBreakingChanges
+  | -- | All changes that could be breaking are unsupported – we don't know if
+    -- there actually are any breaking changes.
+    OnlyUnsupportedChanges
+
+preprocessChanges :: Orientation -> Changes -> ProcessedChanges 'APILevel
+preprocessChanges initialO = P.fromList . fmap process . P.toList
+  where
+    process :: AnItem Behave AnIssue 'APILevel -> AnItem Behave (FunctorTuple (Const Orientation) AnIssue) 'APILevel
+    process (AnItem paths issue) = AnItem paths $ FunctorTuple (Const $ toggle initialO) issue
+      where
+        (Endo toggle) = togglePaths paths
+
+    togglePaths :: Paths Behave a c -> Endo Orientation
+    togglePaths Root = mempty
+    togglePaths (rest `Snoc` (_ :: Behave b c)) = case eqT @c @'ResponseLevel of
+      Just Refl -> Endo toggleOrientation <> togglePaths rest
+      Nothing -> togglePaths rest
+
+generateReport :: ReportInput -> (Pandoc, ReportStatus)
+generateReport inp =
+  let partitionUnsupported = P.partition (\(AnIssue i) -> issueIsUnsupported i)
+      (bUnsupported, preprocessChanges Forward -> breaking) =
+        partitionUnsupported $ breakingChanges inp
+      (nbUnsupported, preprocessChanges Backward -> nonBreaking) =
+        partitionUnsupported $ nonBreakingChanges inp
+      unsupported = preprocessChanges Forward $ bUnsupported <> nbUnsupported
+      breakingChangesPresent = not $ P.null breaking
+      nonBreakingChangesPresent = not $ P.null nonBreaking
+      unsupportedChangesPresent = not $ P.null unsupported
+      report = doc $
+        runReportMonad jets $ do
+          smartHeader "Summary"
+          tell $
+            simpleTable
+              (para
+                 <$> [ refOpt breakingChangesPresent breakingChangesId "⚠️ Breaking changes"
+                     , refOpt nonBreakingChangesPresent nonBreakingChangesId "🙆 Non-breaking changes"
+                     , refOpt unsupportedChangesPresent unsupportedChangesId "🤷 Unsupported feature changes"
+                     ])
+              [para . show' <$> [P.size breaking, P.size nonBreaking, P.size unsupported]]
+          when breakingChangesPresent $ do
+            smartHeader $ anchor breakingChangesId <> "⚠️ Breaking changes"
+            incrementHeaders $ showErrs breaking
+          when nonBreakingChangesPresent $ do
+            smartHeader $ anchor nonBreakingChangesId <> "🙆 Non-breaking changes"
+            incrementHeaders $ showErrs nonBreaking
+          when unsupportedChangesPresent $ do
+            smartHeader $ anchor unsupportedChangesId <> "🤷 Unsupported feature changes"
+            incrementHeaders $ showErrs unsupported
+      status =
+        if
+            | breakingChangesPresent -> BreakingChanges
+            | unsupportedChangesPresent -> OnlyUnsupportedChanges
+            | otherwise -> NoBreakingChanges
+   in (report, status)
   where
     anchor :: Text -> Inlines
     anchor a = spanWith (a, [], []) mempty
@@ -60,11 +118,10 @@ generateReport (Left errs) = doc $
     refOpt False _ i = i
     refOpt True a i = link ("#" <> a) "" i
 
-    breakingChangesId :: Text
+    breakingChangesId, nonBreakingChangesId, unsupportedChangesId :: Text
     breakingChangesId = "breaking-changes"
-
-    unsupportedChangesId :: Text
     unsupportedChangesId = "unsupported-changes"
+    nonBreakingChangesId = "non-breaking-changes"
 
 data ReportState = ReportState
   { sourceJets :: [ReportJet' Behave Inlines]
@@ -88,22 +145,24 @@ smartHeader i = do
   h <- asks headerLevel
   tell $ header h i
 
-showErrs :: forall a. Typeable a => P.PathsPrefixTree Behave AnIssue a -> ReportMonad ()
+showErrs :: forall a. Typeable a => ProcessedChanges a -> ReportMonad ()
 showErrs x@(P.PathsPrefixNode currentIssues _) = do
   let -- Extract this pattern if more cases like this arise
-      (removedPaths :: [Issue 'APILevel], otherIssues :: Set (AnIssue a)) = case eqT @a @'APILevel of
-        Just Refl ->
-          let (p, o) =
-                S.partition
-                  (\(AnIssue u) -> case u of
-                     NoPathsMatched {} -> True
-                     AllPathsFailed {} -> True)
-                  currentIssues
-              p' = S.toList p <&> (\(AnIssue i) -> i)
-           in (p', o)
-        Nothing -> (mempty, currentIssues)
+      ( removedPaths :: [Issue 'APILevel]
+        , otherIssues :: Set (FunctorTuple (Const Orientation) AnIssue a)
+        ) = case eqT @a @'APILevel of
+          Just Refl ->
+            let (p, o) =
+                  S.partition
+                    (\(FunctorTuple _ (AnIssue u)) -> case u of
+                       NoPathsMatched {} -> True
+                       AllPathsFailed {} -> True)
+                    currentIssues
+                p' = S.toList p <&> (\(FunctorTuple _ (AnIssue i)) -> i)
+             in (p', o)
+          Nothing -> (mempty, currentIssues)
   jts <- asks sourceJets
-  for_ otherIssues $ \(AnIssue i) -> tell . describeIssue $ i
+  for_ otherIssues $ \(FunctorTuple (Const ori) (AnIssue i)) -> tell . describeIssue ori $ i
   unless ([] == removedPaths) $ do
     smartHeader "Removed paths"
     tell $
@@ -135,9 +194,9 @@ jets =
     <$> [ constructReportJet jsonPathJet
         , constructReportJet $ \p@(AtPath _) op@(InOperation _) ->
             strong (describeBehaviour op) <> " " <> describeBehaviour p :: Inlines
-        , constructReportJet $ \InRequest InPayload PayloadSchema -> "JSON Request" :: Inlines
+        , constructReportJet $ \InRequest InPayload PayloadSchema -> "📱➡️ JSON Request" :: Inlines
         , constructReportJet $ \(WithStatusCode c) ResponsePayload PayloadSchema ->
-            "JSON Response – " <> str (T.pack . show $ c) :: Inlines
+            "📱⬅️ JSON Response – " <> str (T.pack . show $ c) :: Inlines
         ]
   where
     unwrapReportJetResult :: ReportJetResult Behave x -> ReportJet' Behave x
@@ -177,8 +236,8 @@ jets =
 
 observeJetShowErrs
   :: ReportJet' Behave Inlines
-  -> P.PathsPrefixTree Behave AnIssue a
-  -> ReportMonad (P.PathsPrefixTree Behave AnIssue a)
+  -> ProcessedChanges a
+  -> ReportMonad (ProcessedChanges a)
 observeJetShowErrs jet p = case observeJetShowErrs' jet p of
   Just m -> m
   Nothing -> pure p
@@ -186,8 +245,8 @@ observeJetShowErrs jet p = case observeJetShowErrs' jet p of
 observeJetShowErrs'
   :: forall a.
      ReportJet' Behave Inlines
-  -> P.PathsPrefixTree Behave AnIssue a
-  -> Maybe (ReportMonad (P.PathsPrefixTree Behave AnIssue a))
+  -> ProcessedChanges a
+  -> Maybe (ReportMonad (ProcessedChanges a))
 observeJetShowErrs' (ReportJet jet) (P.PathsPrefixNode currentIssues subIssues) =
   let results =
         subIssues >>= \(WrapTypeable (AStep m)) ->
diff --git a/src/OpenAPI/Checker/Run.hs b/src/OpenAPI/Checker/Run.hs
new file mode 100644
index 0000000..3c2e67a
--- /dev/null
+++ b/src/OpenAPI/Checker/Run.hs
@@ -0,0 +1,30 @@
+module OpenAPI.Checker.Run
+  ( runChecker
+  , runReport
+  , module OpenAPI.Checker.Report
+  )
+where
+
+import Data.HList
+import Data.OpenApi (OpenApi)
+import OpenAPI.Checker.Paths
+import OpenAPI.Checker.Report
+import OpenAPI.Checker.Subtree
+import OpenAPI.Checker.Validate.OpenApi ()
+
+runChecker :: (OpenApi, OpenApi) -> ReportInput
+runChecker (client, server) =
+  ReportInput
+    { breakingChanges = run client server
+    , nonBreakingChanges = run server client
+    }
+  where
+    toPC p c =
+      ProdCons
+        { producer = traced (step ClientSchema) p
+        , consumer = traced (step ServerSchema) c
+        }
+    run p c = either id mempty . runCompatFormula . checkCompatibility HNil Root $ toPC p c
+
+runReport :: (OpenApi, OpenApi) -> (Pandoc, ReportStatus)
+runReport = generateReport . runChecker
diff --git a/src/OpenAPI/Checker/Subtree/Deriving.hs b/src/OpenAPI/Checker/Subtree/Deriving.hs
deleted file mode 100644
index 5bf7916..0000000
--- a/src/OpenAPI/Checker/Subtree/Deriving.hs
+++ /dev/null
@@ -1,6 +0,0 @@
-module OpenAPI.Checker.Subtree.Deriving (EqSubtree (..)) where
-
-import Control.Monad
-import OpenAPI.Checker.Subtree
-
-newtype EqSubtree t = EqSubtree t
diff --git a/src/OpenAPI/Checker/Validate/Header.hs b/src/OpenAPI/Checker/Validate/Header.hs
index c5dfde2..e6ab657 100644
--- a/src/OpenAPI/Checker/Validate/Header.hs
+++ b/src/OpenAPI/Checker/Validate/Header.hs
@@ -51,9 +51,11 @@ instance Issuable 'HeaderLevel where
     | HeaderSchemaRequired
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
-  describeIssue RequiredHeaderMissing = para "Header has become required."
-  describeIssue NonEmptyHeaderRequired = para "The header does not allow empty values anymore."
-  describeIssue HeaderSchemaRequired = para "Expected header schema, but it is not present."
+  describeIssue Forward RequiredHeaderMissing = para "Header has become required."
+  describeIssue Backward RequiredHeaderMissing = para "Header is no longer required."
+  describeIssue Forward NonEmptyHeaderRequired = para "The header does not allow empty values anymore."
+  describeIssue Backward NonEmptyHeaderRequired = para "The header now allows empty values."
+  describeIssue _ HeaderSchemaRequired = para "Expected header schema, but it is not present."
 
 instance Behavable 'HeaderLevel 'SchemaLevel where
   data Behave 'HeaderLevel 'SchemaLevel
diff --git a/src/OpenAPI/Checker/Validate/Link.hs b/src/OpenAPI/Checker/Validate/Link.hs
index 04ce014..dc0b77e 100644
--- a/src/OpenAPI/Checker/Validate/Link.hs
+++ b/src/OpenAPI/Checker/Validate/Link.hs
@@ -19,4 +19,4 @@ instance Issuable 'LinkLevel where
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported = \case
     LinksUnsupported -> True
-  describeIssue LinksUnsupported = para "OpenApi Diff does not currently support Link Objects."
+  describeIssue _ LinksUnsupported = para "OpenApi Diff does not currently support Link Objects."
diff --git a/src/OpenAPI/Checker/Validate/MediaTypeObject.hs b/src/OpenAPI/Checker/Validate/MediaTypeObject.hs
index 5ea0004..71eaa8b 100644
--- a/src/OpenAPI/Checker/Validate/MediaTypeObject.hs
+++ b/src/OpenAPI/Checker/Validate/MediaTypeObject.hs
@@ -42,9 +42,10 @@ instance Issuable 'PayloadLevel where
     EncodingNotSupported -> True
     _ -> False
 
-  describeIssue MediaTypeSchemaRequired = para "Media type expected, but was not specified."
-  describeIssue (MediaEncodingMissing enc) = para $ "Media encoding " <> str enc <> " added."
-  describeIssue EncodingNotSupported = para "OpenApi Diff does not currently support media encodings other than JSON."
+  describeIssue _ MediaTypeSchemaRequired = para "Media type expected, but was not specified."
+  describeIssue Forward (MediaEncodingMissing enc) = para $ "Media encoding " <> str enc <> " has been removed."
+  describeIssue Backward (MediaEncodingMissing enc) = para $ "Media encoding " <> str enc <> " added."
+  describeIssue _ EncodingNotSupported = para "OpenApi Diff does not currently support media encodings other than JSON."
 
 instance Behavable 'PayloadLevel 'SchemaLevel where
   data Behave 'PayloadLevel 'SchemaLevel
@@ -153,11 +154,16 @@ instance Issuable 'OperationLevel where
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported = \case
     _ -> False
-  describeIssue (ResponseCodeNotFound c) =
+  describeIssue Forward (ResponseCodeNotFound c) =
     para $ "Reponse code " <> (str . T.pack . show $ c) <> " has been added."
-  describeIssue (ParamNotMatched param) =
+  describeIssue Backward (ResponseCodeNotFound c) =
+    para $ "Reponse code " <> (str . T.pack . show $ c) <> " has been removed."
+  describeIssue Forward (ParamNotMatched param) =
     para $ "Parameter " <> code param <> " has become required."
-  describeIssue (PathFragmentNotMatched i) =
+  describeIssue Backward (ParamNotMatched param) =
+    para $ "Parameter " <> code param <> " is no longer required."
+  describeIssue _ (PathFragmentNotMatched i) =
     -- TODO: Indices are meaningless in this context. Replace with a better error.
     para $ "Path fragment " <> (str . T.pack . show $ i) <> " not matched."
-  describeIssue NoRequestBody = para "Request body has been added."
+  describeIssue Forward NoRequestBody = para "Request body has been added."
+  describeIssue Backward NoRequestBody = para "Request body has been removed."
diff --git a/src/OpenAPI/Checker/Validate/OAuth2Flows.hs b/src/OpenAPI/Checker/Validate/OAuth2Flows.hs
index d103540..14e7e3f 100644
--- a/src/OpenAPI/Checker/Validate/OAuth2Flows.hs
+++ b/src/OpenAPI/Checker/Validate/OAuth2Flows.hs
@@ -104,8 +104,9 @@ instance Issuable 'SecurityRequirementLevel where
     | UndefinedSecurityScheme Text
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
-  describeIssue SecurityRequirementNotMet = para "Security scheme has been removed."
-  describeIssue (UndefinedSecurityScheme k) = para $ "Security scheme " <> code k <> " is not defined."
+  describeIssue Forward SecurityRequirementNotMet = para "Security scheme has been removed."
+  describeIssue Backward SecurityRequirementNotMet = para "Security scheme was added."
+  describeIssue _ (UndefinedSecurityScheme k) = para $ "Security scheme " <> code k <> " is not defined."
 
 instance Issuable 'SecuritySchemeLevel where
   data Issue 'SecuritySchemeLevel
@@ -129,26 +130,33 @@ instance Issuable 'SecuritySchemeLevel where
     | ScopeNotDefined Text
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
-  describeIssue RefreshUrlsDontMatch = para "Refresh URL changed."
-  describeIssue (HttpSchemeTypesDontMatch _ _) = para "HTTP scheme type changed."
-  describeIssue (ApiKeyParamsDontMatch _ _) = para "API Key parameters changed."
-  describeIssue (OpenIdConnectUrlsDontMatch _ _) = para "OpenaId Connect URL changed."
-  describeIssue (CustomHttpSchemesDontMatch e a) =
+  describeIssue _ RefreshUrlsDontMatch = para "Refresh URL changed."
+  describeIssue _ (HttpSchemeTypesDontMatch _ _) = para "HTTP scheme type changed."
+  describeIssue _ (ApiKeyParamsDontMatch _ _) = para "API Key parameters changed."
+  describeIssue _ (OpenIdConnectUrlsDontMatch _ _) = para "OpenaId Connect URL changed."
+  describeIssue _ (CustomHttpSchemesDontMatch e a) =
     para $ "Changed HTTP scheme from " <> code e <> " to " <> code a <> "."
-  describeIssue ConsumerDoesNotSupportImplicitFlow = para "Implicit flow support has been removed."
-  describeIssue ConsumerDoesNotSupportPasswordFlow = para "Password flow support has been removed."
-  describeIssue ConsumerDoesNotSupportClientCridentialsFlow = para "Client Cridentials flow support has been removed."
-  describeIssue ConsumerDoesNotSupportAuthorizationCodeFlow = para "Authorization Code flow support has been removed."
-  describeIssue SecuritySchemeNotMatched = para "Security scheme has been removed."
-  describeIssue OAuth2ImplicitFlowNotEqual = para "Implicit Flow changed."
-  describeIssue OAuth2PasswordFlowNotEqual = para "Password Flow changed."
-  describeIssue OAuth2ClientCredentialsFlowNotEqual = para "Client Cridentials Flow changed."
-  describeIssue OAuth2AuthorizationCodeFlowNotEqual = para "Authorization Code Flow changed."
-  describeIssue (ScopesMissing ss) =
+  describeIssue Forward ConsumerDoesNotSupportImplicitFlow = para "Implicit flow support has been removed."
+  describeIssue Backward ConsumerDoesNotSupportImplicitFlow = para "Implicit flow support has been added."
+  describeIssue Forward ConsumerDoesNotSupportPasswordFlow = para "Password flow support has been removed."
+  describeIssue Backward ConsumerDoesNotSupportPasswordFlow = para "Password flow support has been added."
+  describeIssue Forward ConsumerDoesNotSupportClientCridentialsFlow = para "Client Cridentials flow support has been removed."
+  describeIssue Backward ConsumerDoesNotSupportClientCridentialsFlow = para "Client Cridentials flow support has been added."
+  describeIssue Forward ConsumerDoesNotSupportAuthorizationCodeFlow = para "Authorization Code flow support has been removed."
+  describeIssue Backward ConsumerDoesNotSupportAuthorizationCodeFlow = para "Authorization Code flow support has been added."
+  describeIssue Forward SecuritySchemeNotMatched = para "Security scheme has been removed."
+  describeIssue Backward SecuritySchemeNotMatched = para "Security scheme has been added."
+  describeIssue _ OAuth2ImplicitFlowNotEqual = para "Implicit Flow changed."
+  describeIssue _ OAuth2PasswordFlowNotEqual = para "Password Flow changed."
+  describeIssue _ OAuth2ClientCredentialsFlowNotEqual = para "Client Cridentials Flow changed."
+  describeIssue _ OAuth2AuthorizationCodeFlowNotEqual = para "Authorization Code Flow changed."
+  describeIssue Forward (ScopesMissing ss) =
     para "New scopes required:" <> bulletList (S.toList ss <&> codeBlock)
-  describeIssue DifferentSecuritySchemes = para "Completely different security scheme types."
-  describeIssue CanNotHaveScopes = para "The specified security scheme can not have scopes."
-  describeIssue (ScopeNotDefined k) = para $ "Scope with key " <> code k <> " is not defined."
+  describeIssue Backward (ScopesMissing ss) =
+    para "Scopes no longer required:" <> bulletList (S.toList ss <&> codeBlock)
+  describeIssue _ DifferentSecuritySchemes = para "Completely different security scheme types."
+  describeIssue _ CanNotHaveScopes = para "The specified security scheme can not have scopes."
+  describeIssue _ (ScopeNotDefined k) = para $ "Scope with key " <> code k <> " is not defined."
 
 instance Behavable 'SecurityRequirementLevel 'SecuritySchemeLevel where
   data Behave 'SecurityRequirementLevel 'SecuritySchemeLevel
diff --git a/src/OpenAPI/Checker/Validate/Operation.hs b/src/OpenAPI/Checker/Validate/Operation.hs
index 54c5abe..6faccc9 100644
--- a/src/OpenAPI/Checker/Validate/Operation.hs
+++ b/src/OpenAPI/Checker/Validate/Operation.hs
@@ -359,8 +359,10 @@ instance Issuable 'APILevel where
     -- When several paths match given but all checks failed
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
-  describeIssue (NoPathsMatched p) = para $ "The path " <> (code . T.pack) p <> " has been removed."
-  describeIssue (AllPathsFailed p) = para $ "The path " <> (code . T.pack) p <> " has been removed."
+  describeIssue Forward (NoPathsMatched p) = para $ "The path " <> (code . T.pack) p <> " has been removed."
+  describeIssue Backward (NoPathsMatched p) = para $ "The path " <> (code . T.pack) p <> " has been added."
+  describeIssue Forward (AllPathsFailed p) = para $ "The path " <> (code . T.pack) p <> " has been removed."
+  describeIssue Backward (AllPathsFailed p) = para $ "The path " <> (code . T.pack) p <> " has been added."
 
 instance Behavable 'APILevel 'PathLevel where
   data Behave 'APILevel 'PathLevel
@@ -462,7 +464,8 @@ instance Issuable 'PathLevel where
     = OperationMissing OperationMethod
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
-  describeIssue (OperationMissing op) = para $ "Method " <> strong (showMethod op) <> " has been removed."
+  describeIssue Forward (OperationMissing op) = para $ "Method " <> strong (showMethod op) <> " has been removed."
+  describeIssue Backward (OperationMissing op) = para $ "Method " <> strong (showMethod op) <> " has been added."
 
 instance Behavable 'PathLevel 'OperationLevel where
   data Behave 'PathLevel 'OperationLevel
@@ -579,7 +582,7 @@ instance Issuable 'CallbackLevel where
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported = \case
     CallbacksUnsupported -> True
-  describeIssue CallbacksUnsupported = para "OpenApi Diff does not currently support callbacks."
+  describeIssue _ CallbacksUnsupported = para "OpenApi Diff does not currently support callbacks."
 
 tracedCallbackPathItems :: Traced Callback -> Traced ProcessedPathItems
 tracedCallbackPathItems (Traced t (Callback x)) =
diff --git a/src/OpenAPI/Checker/Validate/Param.hs b/src/OpenAPI/Checker/Validate/Param.hs
index 60ae25f..91ea86f 100644
--- a/src/OpenAPI/Checker/Validate/Param.hs
+++ b/src/OpenAPI/Checker/Validate/Param.hs
@@ -69,13 +69,15 @@ instance Issuable 'PathFragmentLevel where
     | PathFragmentsDontMatch Text Text
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
-  describeIssue ParamNameMismatch = para "The path fragments don't match."
-  describeIssue ParamEmptinessIncompatible = para "Expected that an empty parameter is allowed, but it isn't."
-  describeIssue ParamRequired = para "Parameter has become required."
-  describeIssue ParamPlaceIncompatible = para "Parameters in incompatible locations."
-  describeIssue ParamStyleMismatch = para "Different parameter styles (encodings)."
-  describeIssue ParamSchemaMismatch = para "Expected a schema, but didn't find one."
-  describeIssue (PathFragmentsDontMatch e a) = para $ "Parameter changed from " <> code e <> " to " <> code a <> "."
+  describeIssue _ ParamNameMismatch = para "The path fragments don't match."
+  describeIssue Forward ParamEmptinessIncompatible = para "The parameter can no longer be empty."
+  describeIssue Backward ParamEmptinessIncompatible = para "The parameter can now be empty."
+  describeIssue Forward ParamRequired = para "Parameter has become required."
+  describeIssue Backward ParamRequired = para "Parameter is no longer required."
+  describeIssue _ ParamPlaceIncompatible = para "Parameters in incompatible locations."
+  describeIssue _ ParamStyleMismatch = para "Different parameter styles (encodings)."
+  describeIssue _ ParamSchemaMismatch = para "Expected a schema, but didn't find one."
+  describeIssue _ (PathFragmentsDontMatch e a) = para $ "Parameter changed from " <> code e <> " to " <> code a <> "."
 
 instance Behavable 'PathFragmentLevel 'SchemaLevel where
   data Behave 'PathFragmentLevel 'SchemaLevel
diff --git a/src/OpenAPI/Checker/Validate/RequestBody.hs b/src/OpenAPI/Checker/Validate/RequestBody.hs
index 50148fb..fb1291b 100644
--- a/src/OpenAPI/Checker/Validate/RequestBody.hs
+++ b/src/OpenAPI/Checker/Validate/RequestBody.hs
@@ -31,10 +31,14 @@ instance Issuable 'RequestLevel where
     | RequestMediaTypeNotFound MediaType
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
-  describeIssue RequestBodyRequired =
+  describeIssue Forward RequestBodyRequired =
     para "Request body has become required."
-  describeIssue (RequestMediaTypeNotFound t) =
+  describeIssue Backward RequestBodyRequired =
+    para "Request body is no longer required."
+  describeIssue Forward (RequestMediaTypeNotFound t) =
     para $ "Media type " <> (code . T.pack . show $ t) <> " has been removed."
+  describeIssue Backward (RequestMediaTypeNotFound t) =
+    para $ "Media type " <> (code . T.pack . show $ t) <> " has been added."
 
 instance Behavable 'RequestLevel 'PayloadLevel where
   data Behave 'RequestLevel 'PayloadLevel
diff --git a/src/OpenAPI/Checker/Validate/Responses.hs b/src/OpenAPI/Checker/Validate/Responses.hs
index cd79d81..3ab9c91 100644
--- a/src/OpenAPI/Checker/Validate/Responses.hs
+++ b/src/OpenAPI/Checker/Validate/Responses.hs
@@ -72,10 +72,14 @@ instance Issuable 'ResponseLevel where
     | ResponseHeaderMissing HeaderName
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
-  describeIssue (ResponseMediaTypeMissing t) =
+  describeIssue Forward (ResponseMediaTypeMissing t) =
+    para $ "Media type was removed: " <> (code . T.pack . show $ t) <> "."
+  describeIssue Backward (ResponseMediaTypeMissing t) =
     para $ "New media type was added: " <> (code . T.pack . show $ t) <> "."
-  describeIssue (ResponseHeaderMissing h) =
+  describeIssue Forward (ResponseHeaderMissing h) =
     para $ "New header was added " <> code h <> "."
+  describeIssue Backward (ResponseHeaderMissing h) =
+    para $ "Header was removed " <> code h <> "."
 
 instance Behavable 'ResponseLevel 'PayloadLevel where
   data Behave 'ResponseLevel 'PayloadLevel
diff --git a/src/OpenAPI/Checker/Validate/Schema.hs b/src/OpenAPI/Checker/Validate/Schema.hs
index 660b666..d2e1c6f 100644
--- a/src/OpenAPI/Checker/Validate/Schema.hs
+++ b/src/OpenAPI/Checker/Validate/Schema.hs
@@ -1057,38 +1057,58 @@ instance Issuable 'TypedSchemaLevel where
       NoContradiction
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
-  describeIssue (EnumDoesntSatisfy v) = para "The following enum value was added:" <> showJSONValue v
-  describeIssue (NoMatchingEnum v) = para "The following enum value has been removed:" <> showJSONValue v
-  describeIssue (NoMatchingMaximum b) = para $ "Upper bound has been added:" <> showBound b <> "."
-  describeIssue (MatchingMaximumWeak (ProdCons p c)) = para $ "Upper bound changed from " <> showBound p <> " to " <> showBound c <> "."
-  describeIssue (NoMatchingMinimum b) = para $ "Lower bound has been added: " <> showBound b <> "."
-  describeIssue (MatchingMinimumWeak (ProdCons p c)) = para $ "Lower bound changed from " <> showBound p <> " to " <> showBound c <> "."
-  describeIssue (NoMatchingMultipleOf n) = para $ "Value is now a multiple of " <> show' n <> "."
-  describeIssue (MatchingMultipleOfWeak (ProdCons p c)) = para $ "Value changed from being a multiple of " <> show' p <> " to being a multiple of " <> show' c <> "."
-  describeIssue (NoMatchingFormat f) = para $ "Format added: " <> code f <> "."
-  describeIssue (NoMatchingMaxLength n) = para $ "Maximum length added: " <> show' n <> "."
-  describeIssue (MatchingMaxLengthWeak (ProdCons p c)) = para $ "Maximum length of the string changed from " <> show' p <> " to " <> show' c <> "."
-  describeIssue (NoMatchingMinLength n) = para $ "Minimum length of the string added: " <> show' n <> "."
-  describeIssue (MatchingMinLengthWeak (ProdCons p c)) = para $ "Minimum length of the string changed from " <> show' p <> " to " <> show' c <> "."
-  describeIssue (NoMatchingPattern p) = para "Pattern (regular expression) added: " <> codeBlock p
-  describeIssue NoMatchingItems = para "Array item schema has been added."
-  describeIssue (NoMatchingMaxItems n) = para $ "Maximum length of the array has been added " <> show' n <> "."
-  describeIssue (MatchingMaxItemsWeak (ProdCons p c)) = para $ "Maximum length of the array changed from " <> show' p <> " to " <> show' c <> "."
-  describeIssue (NoMatchingMinItems n) = para $ "Minimum length of the array added: " <> show' n <> "."
-  describeIssue (MatchingMinItemsWeak (ProdCons p c)) = para $ "Minimum length of the array changed from " <> show' p <> " to " <> show' c <> "."
-  describeIssue NoMatchingUniqueItems = para "Items are now required to be unique."
-  describeIssue NoMatchingProperties = para "Property added."
-  describeIssue (UnexpectedProperty p) = para $ "Property " <> code p <> " has been removed."
-  describeIssue (PropertyNowRequired p) = para $ "Property " <> code p <> " has become required."
-  describeIssue NoAdditionalProperties = para "Additional properties have been removed."
-  describeIssue (NoMatchingMaxProperties n) = para $ "Maximum number of properties has been added: " <> show' n <> "."
-  describeIssue (MatchingMaxPropertiesWeak (ProdCons p c)) = para $ "Maximum  number of properties has changed from " <> show' p <> " to " <> show' c <> "."
-  describeIssue (NoMatchingMinProperties n) = para $ "Minimum number of properties added: " <> show' n <> "."
-  describeIssue (MatchingMinPropertiesWeak (ProdCons p c)) = para $ "Minimum  number of properties has changed from " <> show' p <> " to " <> show' c <> "."
-  describeIssue (NoMatchingCondition conds) =
+  describeIssue Forward (EnumDoesntSatisfy v) = para "The following enum value was added:" <> showJSONValue v
+  describeIssue Backward (EnumDoesntSatisfy v) = para "The following enum value was removed:" <> showJSONValue v
+  describeIssue Forward (NoMatchingEnum v) = para "The following enum value has been removed:" <> showJSONValue v
+  describeIssue Backward (NoMatchingEnum v) = para "The following enum value has been added:" <> showJSONValue v
+  describeIssue Forward (NoMatchingMaximum b) = para $ "Upper bound has been added:" <> showBound b <> "."
+  describeIssue Backward (NoMatchingMaximum b) = para $ "Upper bound has been removed:" <> showBound b <> "."
+  describeIssue _ (MatchingMaximumWeak (ProdCons p c)) = para $ "Upper bound changed from " <> showBound p <> " to " <> showBound c <> "."
+  describeIssue Forward (NoMatchingMinimum b) = para $ "Lower bound has been added: " <> showBound b <> "."
+  describeIssue Backward (NoMatchingMinimum b) = para $ "Lower bound has been removed: " <> showBound b <> "."
+  describeIssue _ (MatchingMinimumWeak (ProdCons p c)) = para $ "Lower bound changed from " <> showBound p <> " to " <> showBound c <> "."
+  describeIssue Forward (NoMatchingMultipleOf n) = para $ "Value is now a multiple of " <> show' n <> "."
+  describeIssue Backward (NoMatchingMultipleOf n) = para $ "Value is no longer a multiple of " <> show' n <> "."
+  describeIssue _ (MatchingMultipleOfWeak (ProdCons p c)) = para $ "Value changed from being a multiple of " <> show' p <> " to being a multiple of " <> show' c <> "."
+  describeIssue Forward (NoMatchingFormat f) = para $ "Format added: " <> code f <> "."
+  describeIssue Backward (NoMatchingFormat f) = para $ "Format removed: " <> code f <> "."
+  describeIssue Forward (NoMatchingMaxLength n) = para $ "Maximum length added: " <> show' n <> "."
+  describeIssue Backward (NoMatchingMaxLength n) = para $ "Maximum length removed: " <> show' n <> "."
+  describeIssue _ (MatchingMaxLengthWeak (ProdCons p c)) = para $ "Maximum length of the string changed from " <> show' p <> " to " <> show' c <> "."
+  describeIssue Forward (NoMatchingMinLength n) = para $ "Minimum length of the string added: " <> show' n <> "."
+  describeIssue Backward (NoMatchingMinLength n) = para $ "Minimum length of the string removed: " <> show' n <> "."
+  describeIssue _ (MatchingMinLengthWeak (ProdCons p c)) = para $ "Minimum length of the string changed from " <> show' p <> " to " <> show' c <> "."
+  describeIssue Forward (NoMatchingPattern p) = para "Pattern (regular expression) added: " <> codeBlock p
+  describeIssue Backward (NoMatchingPattern p) = para "Pattern (regular expression) removed: " <> codeBlock p
+  describeIssue Forward NoMatchingItems = para "Array item schema has been added."
+  describeIssue Backward NoMatchingItems = para "Array item schema has been removed."
+  describeIssue Forward (NoMatchingMaxItems n) = para $ "Maximum length of the array has been added " <> show' n <> "."
+  describeIssue Backward (NoMatchingMaxItems n) = para $ "Maximum length of the array has been removed " <> show' n <> "."
+  describeIssue _ (MatchingMaxItemsWeak (ProdCons p c)) = para $ "Maximum length of the array changed from " <> show' p <> " to " <> show' c <> "."
+  describeIssue Forward (NoMatchingMinItems n) = para $ "Minimum length of the array added: " <> show' n <> "."
+  describeIssue Backward (NoMatchingMinItems n) = para $ "Minimum length of the array removed: " <> show' n <> "."
+  describeIssue _ (MatchingMinItemsWeak (ProdCons p c)) = para $ "Minimum length of the array changed from " <> show' p <> " to " <> show' c <> "."
+  describeIssue Forward NoMatchingUniqueItems = para "Items are now required to be unique."
+  describeIssue Backward NoMatchingUniqueItems = para "Items are no longer required to be unique."
+  describeIssue Forward NoMatchingProperties = para "Property added."
+  describeIssue Backward NoMatchingProperties = para "Property removed."
+  describeIssue Forward (UnexpectedProperty p) = para $ "Property " <> code p <> " has been removed."
+  describeIssue Backward (UnexpectedProperty p) = para $ "Property " <> code p <> " has been added."
+  describeIssue Forward (PropertyNowRequired p) = para $ "Property " <> code p <> " has become required."
+  describeIssue Backward (PropertyNowRequired p) = para $ "Property " <> code p <> " may not be present."
+  describeIssue Forward NoAdditionalProperties = para "Additional properties have been removed."
+  describeIssue Backward NoAdditionalProperties = para "Additional properties have been added."
+  describeIssue Forward (NoMatchingMaxProperties n) = para $ "Maximum number of properties has been added: " <> show' n <> "."
+  describeIssue Backward (NoMatchingMaxProperties n) = para $ "Maximum number of properties has been removed: " <> show' n <> "."
+  describeIssue _ (MatchingMaxPropertiesWeak (ProdCons p c)) = para $ "Maximum  number of properties has changed from " <> show' p <> " to " <> show' c <> "."
+  describeIssue Forward (NoMatchingMinProperties n) = para $ "Minimum number of properties added: " <> show' n <> "."
+  describeIssue Backward (NoMatchingMinProperties n) = para $ "Minimum number of properties removed: " <> show' n <> "."
+  describeIssue _ (MatchingMinPropertiesWeak (ProdCons p c)) = para $ "Minimum  number of properties has changed from " <> show' p <> " to " <> show' c <> "."
+  describeIssue _ (NoMatchingCondition conds) =
     para "Expected the following conditions to hold, but they didn't (please file a bug if you see this):"
       <> bulletList ((\(SomeCondition c) -> showCondition c) <$> conds)
-  describeIssue NoContradiction = para "The type has been removed."
+  describeIssue Forward NoContradiction = para "The type has been removed."
+  describeIssue Backward NoContradiction = para "The type has been added."
 
 showJSONValue :: A.Value -> Blocks
 showJSONValue v = codeBlockWith ("", ["json"], mempty) (T.decodeUtf8 . BSL.toStrict . A.encode $ v)
@@ -1111,11 +1131,11 @@ instance Issuable 'SchemaLevel where
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = True
 
-  describeIssue (NotSupported i) =
+  describeIssue _ (NotSupported i) =
     para (emph "Encountered a feature that OpenApi Diff does not support: " <> text i <> ".")
-  describeIssue (InvalidSchema i) =
+  describeIssue _ (InvalidSchema i) =
     para (emph "The schema is invalid: " <> text i <> ".")
-  describeIssue UnguardedRecursion =
+  describeIssue _ UnguardedRecursion =
     para "Encountered recursion that is too complex for OpenApi Diff to untangle."
 
 instance Behavable 'SchemaLevel 'TypedSchemaLevel where
diff --git a/src/OpenAPI/Checker/Validate/Server.hs b/src/OpenAPI/Checker/Validate/Server.hs
index 7cf5798..b4d68ce 100644
--- a/src/OpenAPI/Checker/Validate/Server.hs
+++ b/src/OpenAPI/Checker/Validate/Server.hs
@@ -134,13 +134,18 @@ instance Issuable 'ServerLevel where
     | ServerNotMatched
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
-  describeIssue (EnumValueNotConsumed _ v) =
+  describeIssue Forward (EnumValueNotConsumed _ v) =
     para $ "Enum value " <> code v <> " has been removed."
-  describeIssue (ConsumerNotOpen _) =
+  describeIssue Backward (EnumValueNotConsumed _ v) =
+    para $ "Enum value " <> code v <> " has been added."
+  describeIssue Forward (ConsumerNotOpen _) =
     para $ "A variable has been changed from being open to being closed."
-  describeIssue (ServerVariableNotDefined k) =
+  describeIssue Backward (ConsumerNotOpen _) =
+    para $ "A variable has been changed from being closed to being open."
+  describeIssue _ (ServerVariableNotDefined k) =
     para $ "Variable " <> code k <> " is not defined."
-  describeIssue ServerNotMatched = para $ "The server was removed."
+  describeIssue Forward ServerNotMatched = para $ "The server was removed."
+  describeIssue Backward ServerNotMatched = para $ "The server was added."
 
 instance Subtree ProcessedServer where
   type SubtreeLevel ProcessedServer = 'ServerLevel
diff --git a/stack.yaml b/stack.yaml
index 81538bb..60cb077 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,4 +1,4 @@
-resolver: nightly-2021-06-10
+resolver: lts-18.0
 
 extra-deps:
   - open-union-0.4.0.0
diff --git a/stack.yaml.lock b/stack.yaml.lock
index 3c461b6..141b324 100644
--- a/stack.yaml.lock
+++ b/stack.yaml.lock
@@ -20,7 +20,7 @@ packages:
     hackage: type-fun-0.1.3
 snapshots:
 - completed:
-    size: 585361
-    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/nightly/2021/6/10.yaml
-    sha256: ef53458d54ca6084c6d8eb5219d03b38878e999af607cf006d5be86669d9a696
-  original: nightly-2021-06-10
+    size: 585393
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/18/0.yaml
+    sha256: c632012da648385b9fa3c29f4e0afd56ead299f1c5528ee789058be410e883c0
+  original: lts-18.0
diff --git a/test/Spec.hs b/test/Spec.hs
index 128e8bf..7bdcd77 100644
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -9,4 +9,4 @@ main = defaultMain =<< tests
 tests :: IO TestTree
 tests = do
   goldenReportTree <- Spec.Golden.TraceTree.tests
-  return . localOption (mkTimeout 1000000) $ goldenReportTree
+  return . localOption (mkTimeout 5000000) $ goldenReportTree
diff --git a/test/Spec/Golden/TraceTree.hs b/test/Spec/Golden/TraceTree.hs
index 3950de0..34ce818 100644
--- a/test/Spec/Golden/TraceTree.hs
+++ b/test/Spec/Golden/TraceTree.hs
@@ -7,16 +7,10 @@ import Control.Category
 import Control.Exception
 import qualified Data.ByteString.Lazy as BSL
 import Data.Default
-import Data.HList
-import Data.OpenApi
 import Data.Text (Text)
 import qualified Data.Text.Encoding as T
 import qualified Data.Yaml as Yaml
-import OpenAPI.Checker.Behavior
-import OpenAPI.Checker.Paths
-import OpenAPI.Checker.PathsPrefixTree
-import OpenAPI.Checker.Report
-import OpenAPI.Checker.Subtree
+import OpenAPI.Checker.Run
 import OpenAPI.Checker.Validate.OpenApi ()
 import Spec.Golden.Extra
 import Test.Tasty (TestTree, testGroup)
@@ -43,18 +37,9 @@ tests = do
       "report.md"
       ("a.yaml", "b.yaml")
       Yaml.decodeFileThrow
-      (runPandoc . writeMarkdown def {writerExtensions = githubMarkdownExtensions} . generateReport . runChecker)
+      (runPandoc . writeMarkdown def {writerExtensions = githubMarkdownExtensions} . fst . runReport)
 
   return $ testGroup "Golden tests" [traceTreeTests, reportTests]
 
 runPandoc :: PandocPure Text -> IO BSL.ByteString
 runPandoc = either throwIO (pure . BSL.fromStrict . T.encodeUtf8) . runPure
-
-runChecker :: (OpenApi, OpenApi) -> Either (PathsPrefixTree Behave AnIssue 'APILevel) ()
-runChecker = runCompatFormula . checkCompatibility HNil Root . toPC
-  where
-    toPC (c, s) =
-      ProdCons
-        { producer = traced (step ClientSchema) c
-        , consumer = traced (step ServerSchema) s
-        }
diff --git a/test/golden/common/enum-anyof/report.md b/test/golden/common/enum-anyof/report.md
index 4211f70..70b7698 100644
--- a/test/golden/common/enum-anyof/report.md
+++ b/test/golden/common/enum-anyof/report.md
@@ -1 +1,5 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|---------------------|------------------------|-------------------------------|
+| 0                   | 0                      | 0                             |
diff --git a/test/golden/common/enum-anyof/trace-tree.yaml b/test/golden/common/enum-anyof/trace-tree.yaml
index 5d14c1e..b9b681e 100644
--- a/test/golden/common/enum-anyof/trace-tree.yaml
+++ b/test/golden/common/enum-anyof/trace-tree.yaml
@@ -1 +1,2 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges: {}
diff --git a/test/golden/common/id/report.md b/test/golden/common/id/report.md
index 4211f70..70b7698 100644
--- a/test/golden/common/id/report.md
+++ b/test/golden/common/id/report.md
@@ -1 +1,5 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|---------------------|------------------------|-------------------------------|
+| 0                   | 0                      | 0                             |
diff --git a/test/golden/common/id/trace-tree.yaml b/test/golden/common/id/trace-tree.yaml
index 5d14c1e..b9b681e 100644
--- a/test/golden/common/id/trace-tree.yaml
+++ b/test/golden/common/id/trace-tree.yaml
@@ -1 +1,2 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges: {}
diff --git a/test/golden/common/json/recursive/report.md b/test/golden/common/json/recursive/report.md
index 4211f70..70b7698 100644
--- a/test/golden/common/json/recursive/report.md
+++ b/test/golden/common/json/recursive/report.md
@@ -1 +1,5 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|---------------------|------------------------|-------------------------------|
+| 0                   | 0                      | 0                             |
diff --git a/test/golden/common/json/recursive/trace-tree.yaml b/test/golden/common/json/recursive/trace-tree.yaml
index 5d14c1e..b9b681e 100644
--- a/test/golden/common/json/recursive/trace-tree.yaml
+++ b/test/golden/common/json/recursive/trace-tree.yaml
@@ -1 +1,2 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges: {}
diff --git a/test/golden/common/maximum-lowered/report.md b/test/golden/common/maximum-lowered/report.md
index 199513a..186cd0c 100644
--- a/test/golden/common/maximum-lowered/report.md
+++ b/test/golden/common/maximum-lowered/report.md
@@ -1,14 +1,24 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|------------------------------------------|-------------------------------------------------|-------------------------------|
+| 1                                        | 1                                               | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
 ## **POST** /test
 
-### JSON Request
+### 📱➡️ JSON Request
+
+#### `$(Number)`
+
+Upper bound changed from 3.0 inclusive to 2.0 inclusive.
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### 📱⬅️ JSON Response – 200
 
 #### `$(Number)`
 
diff --git a/test/golden/common/maximum-lowered/trace-tree.yaml b/test/golden/common/maximum-lowered/trace-tree.yaml
index bddbc8b..fae9fd7 100644
--- a/test/golden/common/maximum-lowered/trace-tree.yaml
+++ b/test/golden/common/maximum-lowered/trace-tree.yaml
@@ -1,4 +1,4 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       InRequest:
@@ -6,3 +6,11 @@ Left:
           PayloadSchema:
             OfType Number: MatchingMaximumWeak (ProdCons {producer = Inclusive 3.0,
               consumer = Inclusive 2.0})
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      WithStatusCode 200:
+        ResponsePayload:
+          PayloadSchema:
+            OfType Number: MatchingMaximumWeak (ProdCons {producer = Inclusive 3.0,
+              consumer = Inclusive 2.0})
diff --git a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/report.md b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/report.md
index b788d40..084ed09 100644
--- a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/report.md
+++ b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/report.md
@@ -1,8 +1,8 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|------------------------------------------|------------------------|-------------------------------|
+| 1                                        | 0                      | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
@@ -10,4 +10,4 @@
 
 ### Parameter test1
 
-Expected that an empty parameter is allowed, but it isn't.
+The parameter can no longer be empty.
diff --git a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/trace-tree.yaml
index 52a0aff..84ebe69 100644
--- a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/trace-tree.yaml
@@ -1,4 +1,5 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       InParam "test1": ParamEmptinessIncompatible
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/set/report.md b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/set/report.md
index 4211f70..df37459 100644
--- a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/set/report.md
+++ b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/set/report.md
@@ -1 +1,13 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|---------------------|-------------------------------------------------|-------------------------------|
+| 0                   | 1                                               | 0                             |
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### Parameter test1
+
+The parameter can now be empty.
diff --git a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/set/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/set/trace-tree.yaml
index 5d14c1e..84d21b9 100644
--- a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/set/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/set/trace-tree.yaml
@@ -1 +1,5 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      InParam "test1": ParamEmptinessIncompatible
diff --git a/test/golden/common/pathItem/operation/parameters/change/report.md b/test/golden/common/pathItem/operation/parameters/change/report.md
index 2d9c3ec..24ee5e4 100644
--- a/test/golden/common/pathItem/operation/parameters/change/report.md
+++ b/test/golden/common/pathItem/operation/parameters/change/report.md
@@ -1,8 +1,8 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|------------------------------------------|-------------------------------------------------|-------------------------------|
+| 1                                        | 1                                               | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
@@ -15,3 +15,15 @@
 ##### `$(String)`
 
 The type has been removed.
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### Parameter test
+
+#### JSON Schema
+
+##### `$(Number)`
+
+The type has been added.
diff --git a/test/golden/common/pathItem/operation/parameters/change/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/change/trace-tree.yaml
index a2eb624..a9d1cb9 100644
--- a/test/golden/common/pathItem/operation/parameters/change/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/change/trace-tree.yaml
@@ -1,6 +1,12 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       InParam "test":
         InParamSchema:
           OfType String: NoContradiction
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      InParam "test":
+        InParamSchema:
+          OfType Number: NoContradiction
diff --git a/test/golden/common/pathItem/operation/parameters/required/false/add/report.md b/test/golden/common/pathItem/operation/parameters/required/false/add/report.md
index 4211f70..70b7698 100644
--- a/test/golden/common/pathItem/operation/parameters/required/false/add/report.md
+++ b/test/golden/common/pathItem/operation/parameters/required/false/add/report.md
@@ -1 +1,5 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|---------------------|------------------------|-------------------------------|
+| 0                   | 0                      | 0                             |
diff --git a/test/golden/common/pathItem/operation/parameters/required/false/add/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/required/false/add/trace-tree.yaml
index 5d14c1e..b9b681e 100644
--- a/test/golden/common/pathItem/operation/parameters/required/false/add/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/required/false/add/trace-tree.yaml
@@ -1 +1,2 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/parameters/required/false/del/report.md b/test/golden/common/pathItem/operation/parameters/required/false/del/report.md
index 4211f70..70b7698 100644
--- a/test/golden/common/pathItem/operation/parameters/required/false/del/report.md
+++ b/test/golden/common/pathItem/operation/parameters/required/false/del/report.md
@@ -1 +1,5 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|---------------------|------------------------|-------------------------------|
+| 0                   | 0                      | 0                             |
diff --git a/test/golden/common/pathItem/operation/parameters/required/false/del/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/required/false/del/trace-tree.yaml
index 5d14c1e..b9b681e 100644
--- a/test/golden/common/pathItem/operation/parameters/required/false/del/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/required/false/del/trace-tree.yaml
@@ -1 +1,2 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/parameters/required/reset/report.md b/test/golden/common/pathItem/operation/parameters/required/reset/report.md
index 4211f70..6fedc96 100644
--- a/test/golden/common/pathItem/operation/parameters/required/reset/report.md
+++ b/test/golden/common/pathItem/operation/parameters/required/reset/report.md
@@ -1 +1,13 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|---------------------|-------------------------------------------------|-------------------------------|
+| 0                   | 1                                               | 0                             |
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### Parameter test1
+
+Parameter is no longer required.
diff --git a/test/golden/common/pathItem/operation/parameters/required/reset/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/required/reset/trace-tree.yaml
index 5d14c1e..c898388 100644
--- a/test/golden/common/pathItem/operation/parameters/required/reset/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/required/reset/trace-tree.yaml
@@ -1 +1,5 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      InParam "test1": ParamRequired
diff --git a/test/golden/common/pathItem/operation/parameters/required/set/report.md b/test/golden/common/pathItem/operation/parameters/required/set/report.md
index 3a58d19..cded916 100644
--- a/test/golden/common/pathItem/operation/parameters/required/set/report.md
+++ b/test/golden/common/pathItem/operation/parameters/required/set/report.md
@@ -1,8 +1,8 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|------------------------------------------|------------------------|-------------------------------|
+| 1                                        | 0                      | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
diff --git a/test/golden/common/pathItem/operation/parameters/required/set/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/required/set/trace-tree.yaml
index e484608..7166f59 100644
--- a/test/golden/common/pathItem/operation/parameters/required/set/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/required/set/trace-tree.yaml
@@ -1,4 +1,5 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       InParam "test1": ParamRequired
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/parameters/required/true/add/report.md b/test/golden/common/pathItem/operation/parameters/required/true/add/report.md
index 6817026..d8c6989 100644
--- a/test/golden/common/pathItem/operation/parameters/required/true/add/report.md
+++ b/test/golden/common/pathItem/operation/parameters/required/true/add/report.md
@@ -1,8 +1,8 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|------------------------------------------|------------------------|-------------------------------|
+| 1                                        | 0                      | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
diff --git a/test/golden/common/pathItem/operation/parameters/required/true/add/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/required/true/add/trace-tree.yaml
index e4be5d6..a24a2a6 100644
--- a/test/golden/common/pathItem/operation/parameters/required/true/add/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/required/true/add/trace-tree.yaml
@@ -1,3 +1,4 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod: ParamNotMatched "test2"
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/parameters/required/true/del/report.md b/test/golden/common/pathItem/operation/parameters/required/true/del/report.md
index 4211f70..09f725d 100644
--- a/test/golden/common/pathItem/operation/parameters/required/true/del/report.md
+++ b/test/golden/common/pathItem/operation/parameters/required/true/del/report.md
@@ -1 +1,11 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|---------------------|-------------------------------------------------|-------------------------------|
+| 0                   | 1                                               | 0                             |
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+Parameter `test2` is no longer required.
diff --git a/test/golden/common/pathItem/operation/parameters/required/true/del/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/required/true/del/trace-tree.yaml
index 5d14c1e..02e313b 100644
--- a/test/golden/common/pathItem/operation/parameters/required/true/del/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/required/true/del/trace-tree.yaml
@@ -1 +1,4 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod: ParamNotMatched "test2"
diff --git a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/add/report.md b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/add/report.md
index 4211f70..b07e363 100644
--- a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/add/report.md
+++ b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/add/report.md
@@ -1 +1,13 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|---------------------|-------------------------------------------------|-------------------------------|
+| 0                   | 1                                               | 0                             |
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### Request
+
+Media type `application/x-www-form-urlencoded` has been added.
diff --git a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/add/trace-tree.yaml b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/add/trace-tree.yaml
index 5d14c1e..2e1bb62 100644
--- a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/add/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/add/trace-tree.yaml
@@ -1 +1,5 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      InRequest: RequestMediaTypeNotFound application/x-www-form-urlencoded
diff --git a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/report.md b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/report.md
index 54e2921..05fa47b 100644
--- a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/report.md
+++ b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/report.md
@@ -1,15 +1,25 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|------------------------------------------|-------------------------------------------------|-------------------------------|
+| 1                                        | 1                                               | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
 ## **POST** /test
 
-### JSON Request
+### 📱➡️ JSON Request
 
 #### `$(String)`
 
 The type has been removed.
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### 📱➡️ JSON Request
+
+#### `$(Number)`
+
+The type has been added.
diff --git a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/trace-tree.yaml b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/trace-tree.yaml
index 41b98f9..ced3434 100644
--- a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/trace-tree.yaml
@@ -1,7 +1,14 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       InRequest:
         InPayload:
           PayloadSchema:
             OfType String: NoContradiction
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      InRequest:
+        InPayload:
+          PayloadSchema:
+            OfType Number: NoContradiction
diff --git a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/report.md b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/report.md
index 63b6dfb..b8feef4 100644
--- a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/report.md
+++ b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/report.md
@@ -1,8 +1,8 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|------------------------------------------|------------------------|-------------------------------|
+| 1                                        | 0                      | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
diff --git a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/trace-tree.yaml b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/trace-tree.yaml
index 3b6684f..2515517 100644
--- a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/trace-tree.yaml
@@ -1,4 +1,5 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       InRequest: RequestMediaTypeNotFound application/x-www-form-urlencoded
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/requestBody/required/reset/report.md b/test/golden/common/pathItem/operation/requestBody/required/reset/report.md
index 4211f70..ebe67f6 100644
--- a/test/golden/common/pathItem/operation/requestBody/required/reset/report.md
+++ b/test/golden/common/pathItem/operation/requestBody/required/reset/report.md
@@ -1 +1,13 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|---------------------|-------------------------------------------------|-------------------------------|
+| 0                   | 1                                               | 0                             |
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### Request
+
+Request body is no longer required.
diff --git a/test/golden/common/pathItem/operation/requestBody/required/reset/trace-tree.yaml b/test/golden/common/pathItem/operation/requestBody/required/reset/trace-tree.yaml
index 5d14c1e..0c5d8ad 100644
--- a/test/golden/common/pathItem/operation/requestBody/required/reset/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/requestBody/required/reset/trace-tree.yaml
@@ -1 +1,5 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      InRequest: RequestBodyRequired
diff --git a/test/golden/common/pathItem/operation/requestBody/required/set/report.md b/test/golden/common/pathItem/operation/requestBody/required/set/report.md
index c38e075..73beda5 100644
--- a/test/golden/common/pathItem/operation/requestBody/required/set/report.md
+++ b/test/golden/common/pathItem/operation/requestBody/required/set/report.md
@@ -1,8 +1,8 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|------------------------------------------|------------------------|-------------------------------|
+| 1                                        | 0                      | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
diff --git a/test/golden/common/pathItem/operation/requestBody/required/set/trace-tree.yaml b/test/golden/common/pathItem/operation/requestBody/required/set/trace-tree.yaml
index 759e4f9..b3fc0c3 100644
--- a/test/golden/common/pathItem/operation/requestBody/required/set/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/requestBody/required/set/trace-tree.yaml
@@ -1,4 +1,5 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       InRequest: RequestBodyRequired
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/responses/add/report.md b/test/golden/common/pathItem/operation/responses/add/report.md
index db889ce..6b7791f 100644
--- a/test/golden/common/pathItem/operation/responses/add/report.md
+++ b/test/golden/common/pathItem/operation/responses/add/report.md
@@ -1,8 +1,8 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|------------------------------------------|------------------------|-------------------------------|
+| 1                                        | 0                      | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
diff --git a/test/golden/common/pathItem/operation/responses/add/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/add/trace-tree.yaml
index ea7c116..3794904 100644
--- a/test/golden/common/pathItem/operation/responses/add/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/add/trace-tree.yaml
@@ -1,3 +1,4 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod: ResponseCodeNotFound 500
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/add/report.md b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/add/report.md
index 4211f70..6e05bde 100644
--- a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/add/report.md
+++ b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/add/report.md
@@ -1 +1,13 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|---------------------|-------------------------------------------------|-------------------------------|
+| 0                   | 1                                               | 0                             |
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### Response code 200
+
+New header was added `Test2`.
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/add/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/add/trace-tree.yaml
index 5d14c1e..7d5c7cf 100644
--- a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/add/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/add/trace-tree.yaml
@@ -1 +1,5 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      WithStatusCode 200: ResponseHeaderMissing "Test2"
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/report.md b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/report.md
index ba901e8..e9aa73b 100644
--- a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/report.md
+++ b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/report.md
@@ -1,8 +1,8 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|------------------------------------------|------------------------|-------------------------------|
+| 1                                        | 0                      | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
@@ -10,4 +10,4 @@
 
 ### Response code 200
 
-New header was added `Test2`.
+Header was removed `Test2`.
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/trace-tree.yaml
index a8f6d76..b92aef2 100644
--- a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/trace-tree.yaml
@@ -1,4 +1,5 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       WithStatusCode 200: ResponseHeaderMissing "Test2"
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/optional/add/report.md b/test/golden/common/pathItem/operation/responses/change/headers/optional/add/report.md
index 4211f70..70b7698 100644
--- a/test/golden/common/pathItem/operation/responses/change/headers/optional/add/report.md
+++ b/test/golden/common/pathItem/operation/responses/change/headers/optional/add/report.md
@@ -1 +1,5 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|---------------------|------------------------|-------------------------------|
+| 0                   | 0                      | 0                             |
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/optional/add/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/change/headers/optional/add/trace-tree.yaml
index 5d14c1e..b9b681e 100644
--- a/test/golden/common/pathItem/operation/responses/change/headers/optional/add/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/change/headers/optional/add/trace-tree.yaml
@@ -1 +1,2 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/optional/del/report.md b/test/golden/common/pathItem/operation/responses/change/headers/optional/del/report.md
index 4211f70..70b7698 100644
--- a/test/golden/common/pathItem/operation/responses/change/headers/optional/del/report.md
+++ b/test/golden/common/pathItem/operation/responses/change/headers/optional/del/report.md
@@ -1 +1,5 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|---------------------|------------------------|-------------------------------|
+| 0                   | 0                      | 0                             |
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/optional/del/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/change/headers/optional/del/trace-tree.yaml
index 5d14c1e..b9b681e 100644
--- a/test/golden/common/pathItem/operation/responses/change/headers/optional/del/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/change/headers/optional/del/trace-tree.yaml
@@ -1 +1,2 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/report.md b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/report.md
index a836e84..1a6632a 100644
--- a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/report.md
+++ b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/report.md
@@ -1,8 +1,8 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | 🙆 Non-breaking changes | 🤷 Unsupported feature changes |
+|------------------------------------------|------------------------|-------------------------------|
+| 1                                        | 0                      | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
diff --git a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/trace-tree.yaml
index 1051d3c..c4dd13c 100644
--- a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/trace-tree.yaml
@@ -1,4 +1,5 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       WithStatusCode 200: ResponseMediaTypeMissing application/x-www-form-urlencoded
+nonBreakingChanges: {}
diff --git a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/report.md b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/report.md
index 9a21882..c66da10 100644
--- a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/report.md
+++ b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/report.md
@@ -1,15 +1,25 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|------------------------------------------|-------------------------------------------------|-------------------------------|
+| 1                                        | 1                                               | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
 ## **POST** /test
 
-### JSON Response – 200
+### 📱⬅️ JSON Response – 200
 
 #### `$(Number)`
 
+The type has been added.
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### 📱⬅️ JSON Response – 200
+
+#### `$(String)`
+
 The type has been removed.
diff --git a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/trace-tree.yaml
index 051d29a..7f00915 100644
--- a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/trace-tree.yaml
@@ -1,7 +1,14 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       WithStatusCode 200:
         ResponsePayload:
           PayloadSchema:
             OfType Number: NoContradiction
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      WithStatusCode 200:
+        ResponsePayload:
+          PayloadSchema:
+            OfType String: NoContradiction
diff --git a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/del/report.md b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/del/report.md
index 4211f70..f3b858f 100644
--- a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/del/report.md
+++ b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/del/report.md
@@ -1 +1,13 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|---------------------|-------------------------------------------------|-------------------------------|
+| 0                   | 1                                               | 0                             |
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### Response code 200
+
+Media type was removed: `application/x-www-form-urlencoded`.
diff --git a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/del/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/del/trace-tree.yaml
index 5d14c1e..100fd97 100644
--- a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/del/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/del/trace-tree.yaml
@@ -1 +1,5 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      WithStatusCode 200: ResponseMediaTypeMissing application/x-www-form-urlencoded
diff --git a/test/golden/common/pathItem/operation/responses/del/report.md b/test/golden/common/pathItem/operation/responses/del/report.md
index 4211f70..5d86dc4 100644
--- a/test/golden/common/pathItem/operation/responses/del/report.md
+++ b/test/golden/common/pathItem/operation/responses/del/report.md
@@ -1 +1,11 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|---------------------|-------------------------------------------------|-------------------------------|
+| 0                   | 1                                               | 0                             |
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+Reponse code 500 has been removed.
diff --git a/test/golden/common/pathItem/operation/responses/del/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/del/trace-tree.yaml
index 5d14c1e..a19b676 100644
--- a/test/golden/common/pathItem/operation/responses/del/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/del/trace-tree.yaml
@@ -1 +1,4 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod: ResponseCodeNotFound 500
diff --git a/test/golden/common/property-removed-additional/a.yaml b/test/golden/common/property-removed-additional/a.yaml
new file mode 100644
index 0000000..2cc1b51
--- /dev/null
+++ b/test/golden/common/property-removed-additional/a.yaml
@@ -0,0 +1,32 @@
+openapi: "3.0.0"
+info:
+  version: 1.0.0
+  title: Test
+servers:
+  - url: http://localhost/
+paths:
+  /test:
+    post:
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: "#/components/schemas/Test"
+      responses:
+        "200":
+          description: test
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Test"
+components:
+  schemas:
+    Test:
+      required:
+        - property1
+        - property2
+      properties:
+        property1:
+          type: string
+        property2:
+          type: number
diff --git a/test/golden/common/property-removed-additional/b.yaml b/test/golden/common/property-removed-additional/b.yaml
new file mode 100644
index 0000000..3e702c8
--- /dev/null
+++ b/test/golden/common/property-removed-additional/b.yaml
@@ -0,0 +1,29 @@
+openapi: "3.0.0"
+info:
+  version: 1.0.0
+  title: Test
+servers:
+  - url: http://localhost/
+paths:
+  /test:
+    post:
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: "#/components/schemas/Test"
+      responses:
+        "200":
+          description: test
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/Test"
+components:
+  schemas:
+    Test:
+      required:
+        - property1
+      properties:
+        property1:
+          type: string
diff --git a/test/golden/common/property-removed-additional/report.md b/test/golden/common/property-removed-additional/report.md
new file mode 100644
index 0000000..ab08c6e
--- /dev/null
+++ b/test/golden/common/property-removed-additional/report.md
@@ -0,0 +1,25 @@
+# Summary
+
+| [⚠️ Breaking changes](#breaking-changes) | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|------------------------------------------|-------------------------------------------------|-------------------------------|
+| 1                                        | 1                                               | 0                             |
+
+# <span id="breaking-changes"></span>⚠️ Breaking changes
+
+## **POST** /test
+
+### 📱⬅️ JSON Response – 200
+
+#### `$(Object)`
+
+Property `property2` may not be present.
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### 📱➡️ JSON Request
+
+#### `$(Object)`
+
+Property `property2` may not be present.
diff --git a/test/golden/common/property-removed-additional/trace-tree.yaml b/test/golden/common/property-removed-additional/trace-tree.yaml
new file mode 100644
index 0000000..3755e39
--- /dev/null
+++ b/test/golden/common/property-removed-additional/trace-tree.yaml
@@ -0,0 +1,14 @@
+breakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      WithStatusCode 200:
+        ResponsePayload:
+          PayloadSchema:
+            OfType Object: PropertyNowRequired "property2"
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      InRequest:
+        InPayload:
+          PayloadSchema:
+            OfType Object: PropertyNowRequired "property2"
diff --git a/test/golden/common/property-removed/report.md b/test/golden/common/property-removed/report.md
index d55e815..ad13022 100644
--- a/test/golden/common/property-removed/report.md
+++ b/test/golden/common/property-removed/report.md
@@ -1,21 +1,37 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 2                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|------------------------------------------|-------------------------------------------------|-------------------------------|
+| 2                                        | 2                                               | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
 ## **POST** /test
 
-### JSON Request
+### 📱➡️ JSON Request
 
 #### `$(Object)`
 
 Property `property2` has been removed.
 
-### JSON Response – 200
+### 📱⬅️ JSON Response – 200
 
 #### `$(Object)`
 
-Property `property2` has become required.
+Property `property2` may not be present.
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### 📱➡️ JSON Request
+
+#### `$(Object)`
+
+Property `property2` may not be present.
+
+### 📱⬅️ JSON Response – 200
+
+#### `$(Object)`
+
+Property `property2` has been removed.
diff --git a/test/golden/common/property-removed/trace-tree.yaml b/test/golden/common/property-removed/trace-tree.yaml
index db439b7..0741f65 100644
--- a/test/golden/common/property-removed/trace-tree.yaml
+++ b/test/golden/common/property-removed/trace-tree.yaml
@@ -1,4 +1,4 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       InRequest:
@@ -9,3 +9,14 @@ Left:
         ResponsePayload:
           PayloadSchema:
             OfType Object: PropertyNowRequired "property2"
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      InRequest:
+        InPayload:
+          PayloadSchema:
+            OfType Object: PropertyNowRequired "property2"
+      WithStatusCode 200:
+        ResponsePayload:
+          PayloadSchema:
+            OfType Object: UnexpectedProperty "property2"
diff --git a/test/golden/common/property-required/report.md b/test/golden/common/property-required/report.md
index 943b3f5..66c038c 100644
--- a/test/golden/common/property-required/report.md
+++ b/test/golden/common/property-required/report.md
@@ -1,14 +1,24 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 1                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|------------------------------------------|-------------------------------------------------|-------------------------------|
+| 1                                        | 1                                               | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
 ## **POST** /test
 
-### JSON Request
+### 📱➡️ JSON Request
+
+#### `$(Object)`
+
+Property `property2` has become required.
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /test
+
+### 📱⬅️ JSON Response – 200
 
 #### `$(Object)`
 
diff --git a/test/golden/common/property-required/trace-tree.yaml b/test/golden/common/property-required/trace-tree.yaml
index 10b4293..949ffb5 100644
--- a/test/golden/common/property-required/trace-tree.yaml
+++ b/test/golden/common/property-required/trace-tree.yaml
@@ -1,7 +1,14 @@
-Left:
+breakingChanges:
   AtPath "/test":
     InOperation PostMethod:
       InRequest:
         InPayload:
           PayloadSchema:
             OfType Object: PropertyNowRequired "property2"
+nonBreakingChanges:
+  AtPath "/test":
+    InOperation PostMethod:
+      WithStatusCode 200:
+        ResponsePayload:
+          PayloadSchema:
+            OfType Object: PropertyNowRequired "property2"
diff --git a/test/golden/common/recursive/report.md b/test/golden/common/recursive/report.md
index 4211f70..5dfc26f 100644
--- a/test/golden/common/recursive/report.md
+++ b/test/golden/common/recursive/report.md
@@ -1 +1,19 @@
-# No breaking changes found ✨
+# Summary
+
+| ⚠️ Breaking changes | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|---------------------|-------------------------------------------------|-------------------------------|
+| 0                   | 1                                               | 0                             |
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **GET** /api/foo
+
+### 📱⬅️ JSON Response – 200
+
+#### `$.leaf.value.foo(String)`
+
+The following enum value has been removed:
+
+``` json
+"a"
+```
diff --git a/test/golden/common/recursive/trace-tree.yaml b/test/golden/common/recursive/trace-tree.yaml
index 5d14c1e..9ce3f0d 100644
--- a/test/golden/common/recursive/trace-tree.yaml
+++ b/test/golden/common/recursive/trace-tree.yaml
@@ -1 +1,14 @@
-Right: []
+breakingChanges: {}
+nonBreakingChanges:
+  AtPath "/api/foo":
+    InOperation GetMethod:
+      WithStatusCode 200:
+        ResponsePayload:
+          PayloadSchema:
+            OfType Object:
+              InProperty "leaf":
+                OfType Object:
+                  InProperty "value":
+                    OfType Object:
+                      InProperty "foo":
+                        OfType String: NoMatchingEnum (String "a")
diff --git a/test/golden/common/security-scheme/report.md b/test/golden/common/security-scheme/report.md
index 4d2c023..b711c46 100644
--- a/test/golden/common/security-scheme/report.md
+++ b/test/golden/common/security-scheme/report.md
@@ -1,8 +1,8 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 2                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|------------------------------------------|-------------------------------------------------|-------------------------------|
+| 2                                        | 1                                               | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
@@ -21,3 +21,13 @@ Security scheme has been removed.
 #### oauth
 
 Security scheme has been removed.
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **POST** /oauth/check
+
+### Security requirement 0
+
+#### spa-oauth
+
+Security scheme has been added.
diff --git a/test/golden/common/security-scheme/trace-tree.yaml b/test/golden/common/security-scheme/trace-tree.yaml
index e2cc7ee..26290d0 100644
--- a/test/golden/common/security-scheme/trace-tree.yaml
+++ b/test/golden/common/security-scheme/trace-tree.yaml
@@ -1,4 +1,4 @@
-Left:
+breakingChanges:
   AtPath "/oauth/sign_out":
     InOperation GetMethod:
       SecurityRequirementStep 1:
@@ -7,3 +7,8 @@ Left:
     InOperation PostMethod:
       SecurityRequirementStep 0:
         SecuritySchemeStep "oauth": SecuritySchemeNotMatched
+nonBreakingChanges:
+  AtPath "/oauth/check":
+    InOperation PostMethod:
+      SecurityRequirementStep 0:
+        SecuritySchemeStep "spa-oauth": SecuritySchemeNotMatched
diff --git a/test/golden/common/servers/report.md b/test/golden/common/servers/report.md
index 2880c9f..d14292e 100644
--- a/test/golden/common/servers/report.md
+++ b/test/golden/common/servers/report.md
@@ -1,8 +1,8 @@
 # Summary
 
-| [⚠️ Breaking changes](#breaking-changes) | 🤷 Unsupported feature changes |
-|------------------------------------------|-------------------------------|
-| 3                                        | 0                             |
+| [⚠️ Breaking changes](#breaking-changes) | [🙆 Non-breaking changes](#non-breaking-changes) | 🤷 Unsupported feature changes |
+|------------------------------------------|-------------------------------------------------|-------------------------------|
+| 3                                        | 1                                               | 0                             |
 
 # <span id="breaking-changes"></span>⚠️ Breaking changes
 
@@ -17,3 +17,11 @@ The server was removed.
 Enum value `a` has been removed.
 
 A variable has been changed from being open to being closed.
+
+# <span id="non-breaking-changes"></span>🙆 Non-breaking changes
+
+## **GET** /pets
+
+### Server `http://{x}variable.path/{y}/{openVariable1}/{openVariable2}`
+
+Enum value `bbb` has been added.
diff --git a/test/golden/common/servers/trace-tree.yaml b/test/golden/common/servers/trace-tree.yaml
index 2b0d629..b504af6 100644
--- a/test/golden/common/servers/trace-tree.yaml
+++ b/test/golden/common/servers/trace-tree.yaml
@@ -1,7 +1,12 @@
-Left:
+breakingChanges:
   AtPath "/pets":
     InOperation GetMethod:
       InServer "http://{x}variable.path/{y}/{openVariable1}/{openVariable2}":
       - EnumValueNotConsumed 1 "a"
       - ConsumerNotOpen 7
       InServer "http://missing.url": ServerNotMatched
+nonBreakingChanges:
+  AtPath "/pets":
+    InOperation GetMethod:
+      InServer "http://{x}variable.path/{y}/{openVariable1}/{openVariable2}": EnumValueNotConsumed
+        3 "bbb"
diff --git a/test/golden/common/unguarded-recursive/report.md b/test/golden/common/unguarded-recursive/report.md
index 1aea61d..43fd067 100644
--- a/test/golden/common/unguarded-recursive/report.md
+++ b/test/golden/common/unguarded-recursive/report.md
@@ -1,13 +1,13 @@
 # Summary
 
-| ⚠️ Breaking changes | [🤷 Unsupported feature changes](#unsupported-changes) |
-|---------------------|-------------------------------------------------------|
-| 0                   | 1                                                     |
+| ⚠️ Breaking changes | 🙆 Non-breaking changes | [🤷 Unsupported feature changes](#unsupported-changes) |
+|---------------------|------------------------|-------------------------------------------------------|
+| 0                   | 0                      | 1                                                     |
 
 # <span id="unsupported-changes"></span>🤷 Unsupported feature changes
 
 ## **GET** /api/foo
 
-### JSON Response – 200
+### 📱⬅️ JSON Response – 200
 
 Encountered recursion that is too complex for OpenApi Diff to untangle.
diff --git a/test/golden/common/unguarded-recursive/trace-tree.yaml b/test/golden/common/unguarded-recursive/trace-tree.yaml
index 590caf5..beb3b6b 100644
--- a/test/golden/common/unguarded-recursive/trace-tree.yaml
+++ b/test/golden/common/unguarded-recursive/trace-tree.yaml
@@ -1,4 +1,10 @@
-Left:
+breakingChanges:
+  AtPath "/api/foo":
+    InOperation GetMethod:
+      WithStatusCode 200:
+        ResponsePayload:
+          PayloadSchema: UnguardedRecursion
+nonBreakingChanges:
   AtPath "/api/foo":
     InOperation GetMethod:
       WithStatusCode 200: