Allow DisplayNameAttribute on classes with parameter substitution support

TUnit.Core/Attributes/TestMetadata/DisplayNameAttribute.cs

@@ -5,30 +5,37 @@
 namespace TUnit.Core;
 
 /// <summary>
-/// Attribute that allows specifying a custom display name for a test method.
+/// Attribute that allows specifying a custom display name for a test method or test class.
 /// </summary>
 /// <remarks>
 /// <para>
-/// This attribute can be applied to test methods to provide more descriptive names than the default method name.
+/// This attribute can be applied to test methods or test classes to provide more descriptive names than the default method or class name.
 /// </para>
 /// <para>
 /// The display name can include parameter placeholders in the format of "$parameterName" which will be
-/// replaced with the actual parameter values during test execution. For example:
+/// replaced with the actual parameter values during test execution. For test methods, method parameters 
+/// will be used for substitution. For test classes, constructor parameters will be used for substitution. For example:
 /// <code>
 /// [Test]
 /// [Arguments("John", 25)]
 /// [DisplayName("User $name is $age years old")]
 /// public void TestUser(string name, int age) { ... }
+/// 
+/// [Arguments("TestData")]
+/// [DisplayName("Class with data: $data")]
+/// public class MyTestClass(string data) { ... }
 /// </code>
 /// </para>
 /// <para>
-/// When this test runs, the display name would appear as "User John is 25 years old".
+/// When these tests run, the display names would appear as "User John is 25 years old" and 
+/// "Class with data: TestData" respectively.
 /// </para>
 /// </remarks>
 /// <param name="displayName">
 /// The display name template. Can include parameter placeholders in the format of "$parameterName".
+/// For methods, method parameter names can be referenced. For classes, constructor parameter names can be referenced.
 /// </param>
-[AttributeUsage(AttributeTargets.Method, Inherited = false)]
+[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, Inherited = false)]
 public sealed class DisplayNameAttribute(string displayName) : DisplayNameFormatterAttribute, IScopedAttribute<DisplayNameAttribute>
 {
     /// <inheritdoc />
@@ -38,17 +45,34 @@ protected override string FormatDisplayName(DiscoveredTestContext context)
 
         var mutableDisplayName = displayName;
 
-        var parameters = testDetails
+        // Try to substitute method parameters first
+        var methodParameters = testDetails
             .MethodMetadata
             .Parameters
             .Zip(testDetails.TestMethodArguments, (parameterInfo, testArgument) => (ParameterInfo: parameterInfo, TestArgument: testArgument));
 
-        foreach (var parameter in parameters)
+        foreach (var parameter in methodParameters)
         {
             mutableDisplayName = mutableDisplayName.Replace($"${parameter.ParameterInfo.Name}",
                 ArgumentFormatter.Format(parameter.TestArgument, context.ArgumentDisplayFormatters));
         }
 
+        // If there are still placeholders and we have class parameters, try to substitute them
+        if (mutableDisplayName.Contains('$') && testDetails.TestClassArguments.Length > 0)
+        {
+            var classParameters = testDetails
+                .MethodMetadata
+                .Class
+                .Parameters
+                .Zip(testDetails.TestClassArguments, (parameterInfo, testArgument) => (ParameterInfo: parameterInfo, TestArgument: testArgument));
+
+            foreach (var parameter in classParameters)
+            {
+                mutableDisplayName = mutableDisplayName.Replace($"${parameter.ParameterInfo.Name}",
+                    ArgumentFormatter.Format(parameter.TestArgument, context.ArgumentDisplayFormatters));
+            }
+        }
+
         return mutableDisplayName;
     }
 }

TUnit.PublicAPI/Tests.Core_Library_Has_No_API_Changes.DotNet8_0.verified.txt

@@ -572,7 +572,7 @@ namespace
         public DiscoveryResult() { }
         public static .DiscoveryResult Empty { get; }
     }
-    [(.Method, Inherited=false)]
+    [(.Class | .Method, Inherited=false)]
     public sealed class DisplayNameAttribute : .DisplayNameFormatterAttribute, .IScopedAttribute, .IScopedAttribute<.DisplayNameAttribute>
     {
         public DisplayNameAttribute(string displayName) { }

TUnit.PublicAPI/Tests.Core_Library_Has_No_API_Changes.DotNet9_0.verified.txt

@@ -572,7 +572,7 @@ namespace
         public DiscoveryResult() { }
         public static .DiscoveryResult Empty { get; }
     }
-    [(.Method, Inherited=false)]
+    [(.Class | .Method, Inherited=false)]
     public sealed class DisplayNameAttribute : .DisplayNameFormatterAttribute, .IScopedAttribute, .IScopedAttribute<.DisplayNameAttribute>
     {
         public DisplayNameAttribute(string displayName) { }

TUnit.PublicAPI/Tests.Core_Library_Has_No_API_Changes.Net4_7.verified.txt

@@ -526,7 +526,7 @@ namespace
         public DiscoveryResult() { }
         public static .DiscoveryResult Empty { get; }
     }
-    [(.Method, Inherited=false)]
+    [(.Class | .Method, Inherited=false)]
     public sealed class DisplayNameAttribute : .DisplayNameFormatterAttribute, .IScopedAttribute, .IScopedAttribute<.DisplayNameAttribute>
     {
         public DisplayNameAttribute(string displayName) { }

TUnit.TestProject/ClassDisplayNameAttributeTests.cs

@@ -0,0 +1,31 @@
+using TUnit.TestProject.Attributes;
+
+namespace TUnit.TestProject;
+
+[EngineTest(ExpectedResult.Pass)]
+[DisplayName("Custom Class Display Name")]
+public class ClassDisplayNameAttributeTests
+{
+    [Test]
+    public async Task Test()
+    {
+        // This test should inherit the class display name as a prefix or part of the test name
+        await Assert.That(TestContext.Current!.GetDisplayName())
+            .DoesNotContain("ClassDisplayNameAttributeTests");
+    }
+}
+
+[EngineTest(ExpectedResult.Pass)]
+[Arguments("TestValue")]
+[DisplayName("Class with parameter: $value")]
+public class ClassDisplayNameWithParametersTests(string value)
+{
+    [Test]
+    public async Task Test()
+    {
+        // This test should show the class display name with parameter substitution
+        var displayName = TestContext.Current!.GetDisplayName();
+        await Assert.That(displayName)
+            .Contains("TestValue");
+    }
+}