Make the MsTest source generator emit an override modifier when the base class has a TestContext property

src/Verify.MSTest.SourceGenerator.Tests/InheritanceTests.HasAttributeOnDerivedClassAndPropertyManuallyDefinedInBase.verified.txt

@@ -12,7 +12,7 @@
 partial class Derived
 {
     [global::System.CodeDom.Compiler.GeneratedCodeAttribute("Verify.MSTest.SourceGenerator", "1.0.0.0")]
-    public global::Microsoft.VisualStudio.TestTools.UnitTesting.TestContext TestContext
+    public override global::Microsoft.VisualStudio.TestTools.UnitTesting.TestContext TestContext
     {
         get => global::VerifyMSTest.Verifier.CurrentTestContext.Value!.TestContext;
         set => global::VerifyMSTest.Verifier.CurrentTestContext.Value = new global::VerifyMSTest.TestExecutionContext(value, GetType());

src/Verify.MSTest.SourceGenerator.Tests/InheritanceTests.HasAttributeOnDerivedClassAndVirtualPropertyManuallyDefinedInBase.verified.txt

@@ -0,0 +1,22 @@
+{
+  Item1: UsesVerify.g.cs,
+  Item2:
+//-----------------------------------------------------
+// This code was generated by a tool.
+//
+// Changes to this file may cause incorrect behavior
+// and will be lost when the code is regenerated.
+// <auto-generated />
+//-----------------------------------------------------
+
+partial class Derived
+{
+    [global::System.CodeDom.Compiler.GeneratedCodeAttribute("Verify.MSTest.SourceGenerator", "1.0.0.0")]
+    public override global::Microsoft.VisualStudio.TestTools.UnitTesting.TestContext TestContext
+    {
+        get => global::VerifyMSTest.Verifier.CurrentTestContext.Value!.TestContext;
+        set => global::VerifyMSTest.Verifier.CurrentTestContext.Value = new global::VerifyMSTest.TestExecutionContext(value, GetType());
+    }
+}
+
+}

src/Verify.MSTest.SourceGenerator.Tests/InheritanceTests.cs

@@ -76,7 +76,29 @@ public partial class Derived : Base
             }
             """;
 
-        return VerifyGenerator(TestDriver.Run(source), ["CS0108"]);
+        return VerifyGenerator(TestDriver.Run(source), ["CS0506"]);
+    }
+
+    [Fact]
+    public Task HasAttributeOnDerivedClassAndVirtualPropertyManuallyDefinedInBase()
+    {
+        var source = """
+            using Microsoft.VisualStudio.TestTools.UnitTesting;
+            using VerifyMSTest;
+
+            public class Base
+            {
+                public virtual TestContext TestContext { get; set; }
+            }
+
+            [TestClass]
+            [UsesVerify]
+            public partial class Derived : Base
+            {
+            }
+            """;
+
+        return VerifyGenerator(TestDriver.Run(source));
     }
 
     [Fact]

src/Verify.MSTest.SourceGenerator/ClassToGenerate.cs

@@ -8,15 +8,17 @@
 /// The built in equality and hash code implementations won't work because this type includes a
 /// collection (which has reference equality semantics), so we must implement them ourselves.
 /// </remarks>
-readonly record struct ClassToGenerate(string? Namespace, string ClassName, ParentClass[] ParentClasses)
+readonly record struct ClassToGenerate(string? Namespace, string ClassName, bool OverrideTestContext, ParentClass[] ParentClasses)
 {
     public string? Namespace { get; } = Namespace;
     public string ClassName { get; } = ClassName;
     public ParentClass[] ParentClasses { get; } = ParentClasses;
+    public bool OverrideTestContext { get; } = OverrideTestContext;
 
     public bool Equals(ClassToGenerate other) =>
         Namespace == other.Namespace &&
         ClassName == other.ClassName &&
+        OverrideTestContext == other.OverrideTestContext &&
         ParentClasses.SequenceEqual(other.ParentClasses);
 
     public override int GetHashCode()
@@ -27,6 +29,7 @@ public override int GetHashCode()
             var hash = 1430287;
             hash = hash * 7302013 ^ (Namespace ?? string.Empty).GetHashCode();
             hash = hash * 7302013 ^ ClassName.GetHashCode();
+            hash = hash * 7302013 ^ OverrideTestContext.GetHashCode();
 
             // Include (up to) the last 8 elements in the hash code to balance performance and specificity.
             // The runtime also does this for structural equality; see

src/Verify.MSTest.SourceGenerator/Emitter.cs

@@ -57,7 +57,9 @@ void WriteClass(ClassToGenerate classToGenerate) =>
             .AppendLine("{")
                 .IncreaseIndent()
                 .AppendLine(GeneratedCodeAttribute)
-                .AppendLine("public global::Microsoft.VisualStudio.TestTools.UnitTesting.TestContext TestContext")
+                .Append("public ")
+                .Append(TestContextModifiers(classToGenerate))
+                .AppendLine("global::Microsoft.VisualStudio.TestTools.UnitTesting.TestContext TestContext")
                 .AppendLine("{")
                     .IncreaseIndent()
                     .AppendLine("get => global::VerifyMSTest.Verifier.CurrentTestContext.Value!.TestContext;")
@@ -81,4 +83,7 @@ public string GenerateExtensionClasses(IReadOnlyCollection<ClassToGenerate> clas
 
         return builder.ToString();
     }
+
+    static string TestContextModifiers(ClassToGenerate classToGenerate)
+        => classToGenerate.OverrideTestContext ? "override " : string.Empty;
 }

src/Verify.MSTest.SourceGenerator/Parser.cs

@@ -6,7 +6,33 @@ static class Parser
         var name = typeSyntax.GetTypeNameWithGenericParameters();
         var parents = GetParentClasses(typeSyntax, cancel);
 
-        return new ClassToGenerate(ns, name, parents);
+        return new ClassToGenerate(
+            Namespace: ns,
+            ClassName: name,
+            OverrideTestContext: BaseClassHasTestContext(typeSymbol),
+            ParentClasses: parents);
+    }
+
+    static bool BaseClassHasTestContext(INamedTypeSymbol typeSymbol) =>
+        BaseClassesOf(typeSymbol)
+            .Any(HasTestContextProperty);
+
+    static bool HasTestContextProperty(INamedTypeSymbol typeSymbol) =>
+        typeSymbol
+                .GetMembers()
+                .OfType<IPropertySymbol>()
+                .Any(property =>
+                    property.Name == "TestContext" &&
+                    property.DeclaredAccessibility == Accessibility.Public);
+
+    static IEnumerable<INamedTypeSymbol> BaseClassesOf(INamedTypeSymbol typeSymbol)
+    {
+        var baseType = typeSymbol.BaseType;
+        while (baseType?.TypeKind == TypeKind.Class)
+        {
+            yield return baseType;
+            baseType = baseType.BaseType;
+        }
     }
 
     static ParentClass[] GetParentClasses(TypeDeclarationSyntax typeSyntax, Cancel cancel)