tests: custom Arbitrary OutputsSpec producing nonempty OutputsSpec_Names

hnix-store-tests/hnix-store-tests.cabal

@@ -51,6 +51,7 @@ library
       base >=4.12 && <5
     , hnix-store-core >= 0.8
     , bytestring
+    , containers
     , crypton
     , dependent-sum > 0.7
     , generic-arbitrary < 1.1
@@ -80,7 +81,5 @@ test-suite props
     , hnix-store-core
     , hnix-store-tests
     , attoparsec
-    , containers
-    , QuickCheck
     , text
     , hspec

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

@@ -3,13 +3,19 @@
 {-# OPTIONS_GHC -Wno-orphans #-}
 module System.Nix.Arbitrary.DerivedPath where
 
-import Test.QuickCheck (Arbitrary)
+import qualified Data.Set
+import Test.QuickCheck (Arbitrary(..), oneof)
 import Test.QuickCheck.Arbitrary.Generic (GenericArbitrary(..))
 import System.Nix.Arbitrary.StorePath ()
-import System.Nix.DerivedPath (DerivedPath, OutputsSpec)
+import System.Nix.DerivedPath (DerivedPath, OutputsSpec(..))
 
-deriving via GenericArbitrary OutputsSpec
-  instance Arbitrary OutputsSpec
+instance Arbitrary OutputsSpec where
+  arbitrary = oneof
+    [ pure OutputsSpec_All
+    ,   OutputsSpec_Names
+      . Data.Set.fromList
+      <$> ((:) <$> arbitrary <*> arbitrary)
+    ]
 
 deriving via GenericArbitrary DerivedPath
   instance Arbitrary DerivedPath

hnix-store-tests/tests/DerivedPathSpec.hs

@@ -1,25 +1,17 @@
 module DerivedPathSpec where
 
-import Test.Hspec (Spec, describe, shouldBe)
+import Test.Hspec (Spec, describe)
 import Test.Hspec.QuickCheck (prop)
-import Test.QuickCheck (Arbitrary(arbitrary), forAll, suchThat)
+import Test.Hspec.Nix (roundtrips)
 
 import System.Nix.Arbitrary ()
-import System.Nix.DerivedPath (DerivedPath(..), OutputsSpec(..))
 
-import qualified Data.Set
 import qualified System.Nix.DerivedPath
 
 spec :: Spec
 spec = do
   describe "DerivedPath" $ do
     prop "roundtrips" $ \sd ->
-      forAll (arbitrary `suchThat` nonEmptyOutputsSpec_Names) $ \p ->
-        System.Nix.DerivedPath.parseDerivedPath sd
-          (System.Nix.DerivedPath.derivedPathToText sd p)
-        `shouldBe` pure p
-  where
-    nonEmptyOutputsSpec_Names :: DerivedPath -> Bool
-    nonEmptyOutputsSpec_Names (DerivedPath_Built _ (OutputsSpec_Names set)) =
-      not $ Data.Set.null set
-    nonEmptyOutputsSpec_Names _ = True
+      roundtrips
+        (System.Nix.DerivedPath.derivedPathToText sd)
+        (System.Nix.DerivedPath.parseDerivedPath sd)