test(member-data): add failing negative promotion test across different interfaces

Author: perkops

test/Atc.Test.Tests/MemberAutoNSubstituteDataAttributeTests.cs

@@ -80,4 +80,35 @@ public void MemberData_SuppliesValueEarlier_ReusedByLaterFrozenParameter(
     {
         yield return [Substitute.For<ISampleInterface>()];
     }
+
+    // Negative promotion scenario
+    // We provide an earlier argument typed as IFirstInterface whose concrete instance also
+    // implements ISecondInterface. The later parameter is [Frozen] ISecondInterface. Desired
+    // invariant: the framework should NOT promote the earlier IFirstInterface value to satisfy
+    // the frozen ISecondInterface; a distinct instance should be generated/injected instead.
+    // Current promotion logic (Type.IsInstanceOfType) is broad and WILL incorrectly reuse it.
+    // This test therefore initially fails (red) and will pass after tightening promotion logic
+    // in the upcoming refactor (shared frozen helper with exact-type matching / index mapping).
+    [Theory]
+    [MemberAutoNSubstituteData(nameof(DualInterfaceProvidedData))]
+    public void MemberData_DifferentInterface_NotPromoted(
+        IFirstInterface first,
+        [Frozen] ISecondInterface second,
+        SecondInterfaceDependant dependant)
+    {
+        first.Should().NotBeNull();
+        second.Should().NotBeNull();
+        dependant.Should().NotBeNull();
+
+        // Guard: dependant wired to the frozen instance.
+        dependant.Dependency.Should().BeSameAs(second);
+
+        // Specification: these should NOT be the same instance
+        second.Should().NotBeSameAs(first);
+    }
+
+    public static IEnumerable<object?[]> DualInterfaceProvidedData()
+    {
+        yield return [new DualInterfaceImpl { Name = "n", Description = "d" }];
+    }
 }

test/Atc.Test.Tests/SampleTypes/DualInterfaceImpl.cs

@@ -0,0 +1,11 @@
+namespace Atc.Test.Tests.SampleTypes;
+
+// Implements both interfaces so underlying instance satisfies each, allowing us to
+// detect overly-broad promotion logic that reuses an earlier IFirstInterface value
+// for a later [Frozen] ISecondInterface parameter.
+public class DualInterfaceImpl : IFirstInterface, ISecondInterface
+{
+    public string? Name { get; set; }
+
+    public string? Description { get; set; }
+}

test/Atc.Test.Tests/SampleTypes/IFirstInterface.cs

@@ -0,0 +1,6 @@
+namespace Atc.Test.Tests.SampleTypes;
+
+public interface IFirstInterface
+{
+    string? Name { get; set; }
+}

test/Atc.Test.Tests/SampleTypes/ISecondInterface.cs

@@ -0,0 +1,6 @@
+namespace Atc.Test.Tests.SampleTypes;
+
+public interface ISecondInterface
+{
+    string? Description { get; set; }
+}

test/Atc.Test.Tests/SampleTypes/SecondInterfaceDependant.cs

@@ -0,0 +1,11 @@
+namespace Atc.Test.Tests.SampleTypes;
+
+public class SecondInterfaceDependant
+{
+    public SecondInterfaceDependant(ISecondInterface dependency)
+    {
+        Dependency = dependency;
+    }
+
+    public ISecondInterface Dependency { get; }
+}