tests: custom Arbitrary BuildResult without Just mempty errorMessage

hnix-store-remote/tests/NixSerializerSpec.hs

@@ -10,7 +10,6 @@ import Test.Hspec (Expectation, Spec, describe, it, parallel, shouldBe)
 import Test.Hspec.QuickCheck (prop)
 import Test.QuickCheck (Gen, arbitrary, forAll, suchThat)
 
-import qualified System.Nix.Build
 import qualified System.Nix.Hash
 
 import System.Nix.Arbitrary ()
@@ -75,9 +74,7 @@ spec = parallel $ do
     prop "mapS" $ roundtripS (mapS (int @Int) byteString)
 
   describe "Complex" $ do
-    prop "BuildResult"
-      $ forAll (arbitrary `suchThat` ((/= Just "") . System.Nix.Build.errorMessage))
-      $ roundtripS buildResult
+    prop "BuildResult" $ roundtripS buildResult
 
     prop "StorePath" $
       roundtripSReader @StoreDir storePath

hnix-store-remote/tests/SerializeSpec.hs

@@ -13,7 +13,6 @@ import Test.QuickCheck (arbitrary, forAll, suchThat)
 
 import qualified Data.Either
 import qualified Data.HashSet
-import qualified System.Nix.Build
 
 import System.Nix.Arbitrary ()
 import System.Nix.Build (BuildMode(..), BuildResult, BuildStatus(..))
@@ -77,9 +76,7 @@ spec = parallel $ do
     prop "Text" $ roundtripS @Text
     prop "BuildMode" $ roundtripS @BuildMode
     prop "BuildStatus" $ roundtripS @BuildStatus
-    it "BuildResult" $
-      forAll (arbitrary `suchThat` ((/= Just "") . System.Nix.Build.errorMessage))
-      $ roundtripS @BuildResult
+    prop "BuildResult" $ roundtripS @BuildResult
 
     prop "ProtoVersion" $ roundtripS @ProtoVersion
 

hnix-store-tests/src/System/Nix/Arbitrary/Build.hs

@@ -4,7 +4,7 @@
 module System.Nix.Arbitrary.Build where
 
 import Data.Text.Arbitrary ()
-import Test.QuickCheck (Arbitrary(..))
+import Test.QuickCheck (Arbitrary(..), suchThat)
 import Test.QuickCheck.Arbitrary.Generic (GenericArbitrary(..))
 import System.Nix.Arbitrary.UTCTime ()
 
@@ -16,5 +16,14 @@ deriving via GenericArbitrary BuildMode
 deriving via GenericArbitrary BuildStatus
   instance Arbitrary BuildStatus
 
-deriving via GenericArbitrary BuildResult
-  instance Arbitrary BuildResult
+instance Arbitrary BuildResult where
+  arbitrary = do
+    status <- arbitrary
+    -- we encode empty errorMessage as Nothing
+    errorMessage <- arbitrary `suchThat` (/= Just mempty)
+    timesBuilt <- arbitrary
+    isNonDeterministic <- arbitrary
+    startTime <- arbitrary
+    stopTime <- arbitrary
+
+    pure $ BuildResult{..}