diff --git a/tests/NoForbiddenWords.elm b/tests/NoForbiddenWords.elm
new file mode 100644
index 00000000..7b826932
--- /dev/null
+++ b/tests/NoForbiddenWords.elm
@@ -0,0 +1,334 @@
+module NoForbiddenWords exposing (rule)
+
+{-|
+
+@docs rule
+
+-}
+
+import Elm.Project as Project exposing (Project)
+import Elm.Syntax.Declaration as Declaration exposing (Declaration)
+import Elm.Syntax.Node exposing (Node(..))
+import Elm.Syntax.Range as Range exposing (Range)
+import Regex exposing (Regex)
+import Review.Rule as Rule exposing (Rule)
+
+
+{-| Forbid certain words in Elm comments, README and elm.json (package summary only).
+
+    config : List Rule
+    config =
+        [ NoForbiddenWords.rule [ "TODO", "- [ ]" ]
+        ]
+
+
+## Failure Examples
+
+Based on the configured words `TODO` and `- [ ]` the following examples would fail:
+
+    -- TODO: Finish writing this function
+
+
+
+Multi-line comments `{- ... -}` and documentation `{-| ... -}` also work:
+
+
+
+    {- Actions
+       - [ ] Documentation
+       - [ ] Tests
+    -}
+
+-}
+rule : List String -> Rule
+rule words =
+    Rule.newProjectRuleSchema "NoForbiddenWords" ()
+        |> Rule.withElmJsonProjectVisitor (elmJsonVisitor words)
+        |> Rule.withReadmeProjectVisitor (readmeVisitor words)
+        |> Rule.withModuleVisitor (moduleVisitor words)
+        |> Rule.withModuleContext
+            { fromModuleToProject = \_ _ () -> ()
+            , fromProjectToModule = \_ _ () -> ()
+            , foldProjectContexts = \() () -> ()
+            }
+        |> Rule.fromProjectRuleSchema
+
+
+
+--- ELM.JSON
+
+
+elmJsonVisitor : List String -> Maybe { elmJsonKey : Rule.ElmJsonKey, project : Project } -> () -> ( List (Rule.Error scope), () )
+elmJsonVisitor words maybeElmJson () =
+    case maybeElmJson of
+        Nothing ->
+            ( [], () )
+
+        Just elmJson ->
+            ( checkElmJson words elmJson, () )
+
+
+checkElmJson : List String -> { elmJsonKey : Rule.ElmJsonKey, project : Project } -> List (Rule.Error scope)
+checkElmJson words { elmJsonKey, project } =
+    case project of
+        Project.Application _ ->
+            []
+
+        Project.Package info ->
+            fastConcatMap (checkElmJsonSummary elmJsonKey info.summary) words
+
+
+checkElmJsonSummary : Rule.ElmJsonKey -> String -> String -> List (Rule.Error scope)
+checkElmJsonSummary elmJsonKey summary word =
+    summary
+        |> stringNode
+        |> ranges word
+        |> List.map (elmJsonSummaryError elmJsonKey word)
+
+
+elmJsonSummaryError : Rule.ElmJsonKey -> String -> Range -> Rule.Error scope
+elmJsonSummaryError elmJsonKey word rangeInSummary =
+    rawElmJsonSummaryError word rangeInSummary
+        |> Rule.errorForElmJson elmJsonKey
+
+
+rawElmJsonSummaryError : String -> Range -> String -> { message : String, details : List String, range : Range }
+rawElmJsonSummaryError word rangeInSummary rawElmJson =
+    { message = "`" ++ word ++ "` is not allowed in elm.json summary."
+    , details =
+        [ "You should review your elm.json and make sure the forbidden word has been removed before publishing your code."
+        ]
+    , range = rawElmJsonSummaryRange rangeInSummary rawElmJson
+    }
+
+
+rawElmJsonSummaryRange : Range -> String -> Range
+rawElmJsonSummaryRange rangeInSummary rawElmJson =
+    rawElmJson
+        |> jsonFieldLocation "summary"
+        |> Maybe.map (rangeAddLocation rangeInSummary)
+        |> Maybe.withDefault startRange
+
+
+
+--- README
+
+
+readmeVisitor : List String -> Maybe { readmeKey : Rule.ReadmeKey, content : String } -> () -> ( List (Rule.Error scope), () )
+readmeVisitor words maybeReadme () =
+    case maybeReadme of
+        Nothing ->
+            ( [], () )
+
+        Just readme ->
+            ( fastConcatMap (checkForbiddenReadmeWord readme) words
+            , ()
+            )
+
+
+checkForbiddenReadmeWord : { readmeKey : Rule.ReadmeKey, content : String } -> String -> List (Rule.Error scope)
+checkForbiddenReadmeWord { readmeKey, content } word =
+    content
+        |> stringNode
+        |> ranges word
+        |> List.map (forbiddenReadmeWordError readmeKey word)
+
+
+forbiddenReadmeWordError : Rule.ReadmeKey -> String -> Range -> Rule.Error scope
+forbiddenReadmeWordError readmeKey word range =
+    Rule.errorForReadme readmeKey
+        { message = "`" ++ word ++ "` is not allowed in README file."
+        , details =
+            [ "You should review this section and make sure the forbidden word has been removed before publishing your code."
+            ]
+        }
+        range
+
+
+
+--- MODULE
+
+
+moduleVisitor :
+    List String
+    -> Rule.ModuleRuleSchema {} ()
+    -> Rule.ModuleRuleSchema { hasAtLeastOneVisitor : () } ()
+moduleVisitor words schema =
+    schema
+        |> Rule.withSimpleCommentsVisitor (commentsVisitor words)
+        |> Rule.withSimpleDeclarationVisitor (declarationVisitor words)
+
+
+commentsVisitor : List String -> List (Node String) -> List (Rule.Error {})
+commentsVisitor words comments =
+    fastConcatMap (commentVisitor words) comments
+
+
+declarationVisitor : List String -> Node Declaration -> List (Rule.Error {})
+declarationVisitor words (Node _ declaration) =
+    case declaration of
+        Declaration.FunctionDeclaration { documentation } ->
+            documentation
+                |> Maybe.map (commentVisitor words)
+                |> Maybe.withDefault []
+
+        Declaration.CustomTypeDeclaration { documentation } ->
+            documentation
+                |> Maybe.map (commentVisitor words)
+                |> Maybe.withDefault []
+
+        Declaration.AliasDeclaration { documentation } ->
+            documentation
+                |> Maybe.map (commentVisitor words)
+                |> Maybe.withDefault []
+
+        _ ->
+            []
+
+
+commentVisitor : List String -> Node String -> List (Rule.Error {})
+commentVisitor words comment =
+    fastConcatMap (checkForbiddenWord comment) words
+
+
+checkForbiddenWord : Node String -> String -> List (Rule.Error {})
+checkForbiddenWord comment word =
+    ranges word comment
+        |> List.map (forbiddenWordError word)
+
+
+
+--- HELPERS
+
+
+stringNode : String -> Node String
+stringNode string =
+    Node startRange string
+
+
+startRange : Range
+startRange =
+    { start = { row = 1, column = 1 }
+    , end = { row = 1, column = 1 }
+    }
+
+
+rangeAddLocation : Range -> Range.Location -> Range
+rangeAddLocation range start =
+    { start =
+        { row = start.row + range.start.row - 1
+        , column = start.column + range.start.column - 1
+        }
+    , end =
+        { row = start.row + range.end.row - 1
+        , column = start.column + range.end.column - 1
+        }
+    }
+
+
+ranges : String -> Node String -> List Range
+ranges needle (Node range haystack) =
+    String.lines haystack
+        |> List.indexedMap (rangesInLine needle range.start)
+        |> fastConcat
+
+
+rangesInLine : String -> Range.Location -> Int -> String -> List Range
+rangesInLine needle start row line =
+    String.indexes needle line
+        |> List.map (rangeFromIndex needle start row)
+
+
+rangeFromIndex : String -> Range.Location -> Int -> Int -> Range
+rangeFromIndex needle start row index =
+    case row of
+        0 ->
+            { start =
+                { row = start.row
+                , column = start.column + index
+                }
+            , end =
+                { row = start.row
+                , column = start.column + index + String.length needle
+                }
+            }
+
+        _ ->
+            { start =
+                { row = start.row + row
+                , column = index + 1
+                }
+            , end =
+                { row = start.row + row
+                , column = index + 1 + String.length needle
+                }
+            }
+
+
+jsonFieldLocation : String -> String -> Maybe Range.Location
+jsonFieldLocation fieldName rawJson =
+    let
+        regex : Regex
+        regex =
+            jsonFieldRegex fieldName
+    in
+    String.lines rawJson
+        |> List.indexedMap (jsonFieldLocationsInLine regex)
+        |> fastConcat
+        |> List.head
+
+
+jsonFieldLocationsInLine : Regex -> Int -> String -> List Range.Location
+jsonFieldLocationsInLine regex row line =
+    Regex.find regex line
+        |> List.map (jsonFieldMatchLocation row)
+
+
+jsonFieldMatchLocation : Int -> Regex.Match -> Range.Location
+jsonFieldMatchLocation row { match, index } =
+    case row of
+        0 ->
+            { row = 1
+            , column = 1 + index + String.length match
+            }
+
+        _ ->
+            { row = row + 1
+            , column = index + 1 + String.length match
+            }
+
+
+jsonFieldRegex : String -> Regex
+jsonFieldRegex fieldName =
+    Regex.fromString ("\"" ++ fieldName ++ "\"\\s?:\\s?\"")
+        |> Maybe.withDefault Regex.never
+
+
+forbiddenWordError : String -> Range -> Rule.Error {}
+forbiddenWordError word range =
+    Rule.error
+        { message = "`" ++ word ++ "` is not allowed in comments."
+        , details =
+            [ "You should review this comment and make sure the forbidden word has been removed before publishing your code."
+            ]
+        }
+        range
+
+
+
+--- List Performance
+
+
+fastConcat : List (List a) -> List a
+fastConcat =
+    List.foldr (++) []
+
+
+fastConcatMap : (a -> List b) -> List a -> List b
+fastConcatMap fn =
+    let
+        helper : a -> List b -> List b
+        helper item acc =
+            fn item ++ acc
+    in
+    List.foldr helper []
diff --git a/tests/Tests/NoForbiddenWords.elm b/tests/Tests/NoForbiddenWords.elm
new file mode 100644
index 00000000..7c4b5c78
--- /dev/null
+++ b/tests/Tests/NoForbiddenWords.elm
@@ -0,0 +1,321 @@
+module Tests.NoForbiddenWords exposing (all)
+
+import Elm.Project
+import Json.Decode as Decode
+import Json.Encode as Encode
+import NoForbiddenWords exposing (rule)
+import Review.Project as Project exposing (Project)
+import Review.Rule
+import Review.Test
+import Test exposing (Test, describe, test)
+
+
+all : Test
+all =
+    describe "NoForbiddenWords"
+        [ test "with no words reports nothing" <|
+            \() ->
+                """
+module A exposing (..)
+-- TODO: Write main
+main = Debug.todo ""
+"""
+                    |> Review.Test.run (rule [])
+                    |> Review.Test.expectNoErrors
+        , test "reports any found words" <|
+            \() ->
+                """
+module A exposing (..)
+-- TODO: Write main
+main = Debug.todo ""
+"""
+                    |> Review.Test.run (rule [ "TODO" ])
+                    |> Review.Test.expectErrors
+                        [ forbiddenWordError "TODO"
+                        ]
+        , test "reports any found words in multi-line comments" <|
+            \() ->
+                """
+module A exposing (..)
+{- The entry point for our project.
+
+TODO: Write main
+
+-}
+main = Debug.todo ""
+"""
+                    |> Review.Test.run (rule [ "TODO" ])
+                    |> Review.Test.expectErrors
+                        [ forbiddenWordError "TODO"
+                        ]
+        , test "reports `-- [ ]` as `- [ ]`" <|
+            \() ->
+                """
+module A exposing (..)
+-- [ ] Documentation
+main = Debug.todo ""
+"""
+                    |> Review.Test.run (rule [ "- [ ]" ])
+                    |> Review.Test.expectErrors
+                        [ forbiddenWordError "- [ ]"
+                        ]
+        , test "reports forbidden words in module documentation" <|
+            \() ->
+                """
+module A exposing (..)
+{-| Module A
+
+TODO: Write the documentation
+-}
+import Foo
+
+main = Debug.todo ""
+"""
+                    |> Review.Test.run (rule [ "TODO" ])
+                    |> Review.Test.expectErrors
+                        [ forbiddenWordError "TODO"
+                        ]
+        , test "reports forbidden words in function documentation" <|
+            \() ->
+                """
+module A exposing (..)
+{-| Module A
+-}
+import Foo
+
+{-| Main
+
+TODO: Write the documentation
+-}
+main = Debug.todo ""
+"""
+                    |> Review.Test.run (rule [ "TODO" ])
+                    |> Review.Test.expectErrors
+                        [ forbiddenWordError "TODO"
+                        ]
+        , test "reports forbidden words in type documentation" <|
+            \() ->
+                """
+module A exposing (..)
+import Foo
+
+{-| Page
+
+TODO: Add more pages
+-}
+type Page
+    = Page
+
+main = Debug.todo ""
+"""
+                    |> Review.Test.run (rule [ "TODO" ])
+                    |> Review.Test.expectErrors
+                        [ forbiddenWordError "TODO"
+                        ]
+        , test "reports forbidden words in type alias documentation" <|
+            \() ->
+                """
+module A exposing (..)
+import Foo
+
+{-| Page
+
+TODO: Add footer
+-}
+type alias Page =
+    { title : String, body : List (Html msg) }
+
+main = Debug.todo ""
+"""
+                    |> Review.Test.run (rule [ "TODO" ])
+                    |> Review.Test.expectErrors
+                        [ forbiddenWordError "TODO"
+                        ]
+        , test "reports forbidden words in port documentation" <|
+            \() ->
+                """
+port module Ports exposing (..)
+import Foo
+
+{-| Save
+
+TODO: Use Json.Encode.Value here.
+-}
+port save : String -> Cmd Msg
+"""
+                    |> Review.Test.run (rule [ "TODO" ])
+                    |> Review.Test.expectErrors
+                        [ forbiddenWordError "TODO"
+                        ]
+        , test "checks forbidden words in README.md" <|
+            \() ->
+                let
+                    project : Project
+                    project =
+                        Project.new
+                            |> Project.addReadme
+                                { path = "README.md"
+                                , content = """
+# My Awesome Project
+
+TODO: Write the readme
+"""
+                                }
+                in
+                """
+module A exposing (..)
+a = 1"""
+                    |> Review.Test.runWithProjectData project (rule [ "TODO" ])
+                    |> Review.Test.expectErrorsForReadme
+                        [ forbiddenWordErrorForReadme "TODO"
+                        ]
+        , test "forbidden words in README.md can be ignored" <|
+            \() ->
+                let
+                    project : Project
+                    project =
+                        Project.new
+                            |> Project.addReadme
+                                { path = "README.md"
+                                , content = """
+# My Awesome Project
+
+TODO: Write the readme
+"""
+                                }
+                in
+                """
+module A exposing (..)
+a = 1"""
+                    |> Review.Test.runWithProjectData project
+                        (rule [ "TODO" ]
+                            |> Review.Rule.ignoreErrorsForFiles [ "README.md" ]
+                        )
+                    |> Review.Test.expectNoErrors
+        , test "checks elm.json summary for forbidden words" <|
+            \() ->
+                let
+                    project : Project
+                    project =
+                        Project.new
+                            |> Project.addElmJson
+                                (packageElmJson
+                                    { summary = "REPLACEME"
+                                    , formatted = True
+                                    }
+                                )
+                in
+                """
+module A exposing (..)
+a = 1"""
+                    |> Review.Test.runWithProjectData project (rule [ "REPLACEME" ])
+                    |> Review.Test.expectErrorsForElmJson
+                        [ forbiddenWordErrorForElmJson "REPLACEME"
+                        ]
+        , test "checks minified elm.json summary for forbidden words" <|
+            \() ->
+                let
+                    project : Project
+                    project =
+                        Project.new
+                            |> Project.addElmJson
+                                (packageElmJson
+                                    { summary = "REPLACEME"
+                                    , formatted = False
+                                    }
+                                )
+                in
+                """
+module A exposing (..)
+a = 1"""
+                    |> Review.Test.runWithProjectData project (rule [ "REPLACEME" ])
+                    |> Review.Test.expectErrorsForElmJson
+                        [ forbiddenWordErrorForElmJson "REPLACEME"
+                        ]
+        ]
+
+
+packageElmJson : { summary : String, formatted : Bool } -> { path : String, raw : String, project : Elm.Project.Project }
+packageElmJson { summary, formatted } =
+    let
+        spaces : number
+        spaces =
+            if formatted then
+                4
+
+            else
+                0
+    in
+    Encode.encode spaces
+        (Encode.object
+            [ ( "type", Encode.string "package" )
+            , ( "name", Encode.string "sparksp/elm-review-new-package" )
+            , ( "summary", Encode.string summary )
+            , ( "license", Encode.string "MIT" )
+            , ( "version", Encode.string "1.0.0" )
+            , ( "exposed-modules", Encode.list Encode.string [ "NoNewPackage" ] )
+            , ( "elm-version", Encode.string "0.19.0 <= v < 0.20.0" )
+            , ( "dependencies"
+              , Encode.object
+                    [ ( "elm/code", Encode.string "1.0.5 <= v <= 2.0.0" )
+                    ]
+              )
+            , ( "test-dependencies", Encode.object [] )
+            ]
+        )
+        |> createElmJson
+
+
+forbiddenWordError : String -> Review.Test.ExpectedError
+forbiddenWordError word =
+    Review.Test.error
+        { message = "`" ++ word ++ "` is not allowed in comments."
+        , details =
+            [ "You should review this comment and make sure the forbidden word has been removed before publishing your code."
+            ]
+        , under = word
+        }
+
+
+forbiddenWordErrorForReadme : String -> Review.Test.ExpectedError
+forbiddenWordErrorForReadme word =
+    Review.Test.error
+        { message = "`" ++ word ++ "` is not allowed in README file."
+        , details =
+            [ "You should review this section and make sure the forbidden word has been removed before publishing your code."
+            ]
+        , under = word
+        }
+
+
+forbiddenWordErrorForElmJson : String -> Review.Test.ExpectedError
+forbiddenWordErrorForElmJson word =
+    Review.Test.error
+        { message = "`" ++ word ++ "` is not allowed in elm.json summary."
+        , details =
+            [ "You should review your elm.json and make sure the forbidden word has been removed before publishing your code."
+            ]
+        , under = word
+        }
+
+
+
+--- HELPERS
+
+
+createElmJson : String -> { path : String, raw : String, project : Elm.Project.Project }
+createElmJson rawElmJson =
+    { path = "elm.json"
+    , raw = rawElmJson
+    , project = createElmJsonProject rawElmJson
+    }
+
+
+createElmJsonProject : String -> Elm.Project.Project
+createElmJsonProject rawElmJson =
+    case Decode.decodeString Elm.Project.decoder rawElmJson of
+        Ok project ->
+            project
+
+        Err error ->
+            Debug.todo ("[elm.json]: " ++ Debug.toString error)