test: more tests for implicit precedence

src/test/ArbitraryDerivingSuite.scala

@@ -48,13 +48,21 @@ class ArbitraryDerivingSuite extends munit.FunSuite:
     equalValues(ComplexADTWithNestedMembers.expectedGen)
   }
 
-  test("Gives precedence to any arbitraries in scope") {
+  test("Gives precedence to any arbitraries in local scope") {
     given arb: Arbitrary[SimpleADT] = Arbitrary(SimpleCaseClass.expectedGen)
     val expectedGen: Gen[AbstractSubClass.SubclassB] =
       arb.arbitrary.map(AbstractSubClass.SubclassB.apply)
     equalValues(expectedGen)
   }
 
+  test("given derivation does not take precedence over existing givens") {
+    equalValues(HasGivenInstances.specialHasGivenInstancesArbitrary.arbitrary)
+  }
+
+  test("given derivation of child-instances does not take precedence over existing givens") {
+    equalValues(HasMemberThatHasGivenInstances.expectedGen)
+  }
+
   // not a hard requirement (just guarding against accidental worsening by refactoring)
   test("supports case classes with up to 27 fields (if -Xmax-inlines=32)") {
     summon[Arbitrary[MaxCaseClass]]

src/test/CogenDerivingSuite.scala

@@ -41,6 +41,14 @@ class CogenDerivingSuite extends munit.ScalaCheckSuite:
     equalValues(CaseClassWithContainers.expectedCogen)
   }
 
+  test("given derivation does not take precedence over existing givens") {
+    equalValues(HasGivenInstances.specialHasGivenInstancesCogen)
+  }
+
+  test("given derivation of child-instances does not take precedence over existing givens") {
+    equalValues(HasMemberThatHasGivenInstances.expectedCogen)
+  }
+
   test("enables derivation of Arbitrary instances for functions") {
     val arbFunction1: Arbitrary[ComplexADTWithNestedMembers => ABC] =
       summon

src/test/ShrinkDerivingSuite.scala

@@ -31,11 +31,11 @@ class ShrinkDerivingSuite extends munit.ScalaCheckSuite:
     equalValues(ABC.expectedShrink)
   }
 
-  property("derivation does not take precedence over existing givens") {
+  property("given derivation does not take precedence over existing givens") {
     equalValues(HasGivenInstances.specialHasGivenInstancesShrink)
   }
 
-  property("derivation of child-instances does not take precedence over existing givens") {
+  property("given derivation of child-instances does not take precedence over existing givens") {
     equalValues(HasMemberThatHasGivenInstances.expectedShrink)
   }
 

src/test/test_classes.scala

@@ -1,5 +1,6 @@
 package io.github.martinhh
 
+import org.scalacheck.Arbitrary
 import org.scalacheck.Arbitrary.arbitrary
 import org.scalacheck.Cogen
 import org.scalacheck.Cogen.perturb
@@ -186,8 +187,15 @@ case class HasGivenInstances(x: Int)
 
 object HasGivenInstances:
 
-  // this is a nonsense-implementation, only here to prove that it takes precedence
-  // over derivation (and over `Shrink.shrinkAny`):
+  // these are a nonsense-implementations, only here to prove that they takes precedence
+  // over/within derivation:
+
+  given specialHasGivenInstancesArbitrary: Arbitrary[HasGivenInstances] =
+    Arbitrary(Gen.const(HasGivenInstances(42)))
+
+  given specialHasGivenInstancesCogen: Cogen[HasGivenInstances] =
+    Cogen(_.x + 1)
+
   @annotation.nowarn("msg=Stream .* is deprecated")
   given specialHasGivenInstancesShrink: Shrink[HasGivenInstances] = Shrink { hgi =>
     (1 to 3).map(i => HasGivenInstances(hgi.x + i)).toStream
@@ -196,6 +204,23 @@ object HasGivenInstances:
 case class HasMemberThatHasGivenInstances(member: HasGivenInstances)
 
 object HasMemberThatHasGivenInstances:
+
+  val expectedGen: Gen[HasMemberThatHasGivenInstances] =
+    HasGivenInstances.specialHasGivenInstancesArbitrary.arbitrary.map(
+      HasMemberThatHasGivenInstances.apply
+    )
+
+  val expectedCogen: Cogen[HasMemberThatHasGivenInstances] =
+    Cogen { (seed, value) =>
+      perturb[Unit](
+        perturb[HasGivenInstances](
+          seed,
+          value.member
+        )(using HasGivenInstances.specialHasGivenInstancesCogen),
+        ()
+      )
+    }
+
   val expectedShrink: Shrink[HasMemberThatHasGivenInstances] =
     Shrink.xmap(HasMemberThatHasGivenInstances.apply, _.member)