Add acceptance tests for duplicate TestMethod and TestClass attributes

[Copilot]

Adds MSTest acceptance tests validating that duplicate attributes derived from TestMethodAttribute and TestClassAttribute are properly detected and reported as failures.

Test Coverage

The tests validate two distinct failure scenarios:

1. Duplicate TestMethod attributes: Test class with both [TestMethod] and custom [MyTestMethod] attributes on the same method, which causes one test to fail while other tests in the class pass
2. Duplicate TestClass attributes: Test class with both [TestClass] and custom [MyTestClass] attributes that should fail with proper error message

Test Structure

Two separate test methods with dedicated test assets provide focused validation:

• DuplicateTestMethodAttribute_ShouldFail: Uses the DuplicateTestMethodAttribute test asset and validates that the exit code is AtLeastOneTestFailed with 1 test passing and 1 test failing
• DuplicateTestClassAttribute_ShouldFail: Uses the DuplicateTestClassAttribute test asset and validates that duplicate TestClass attributes cause a failure with the expected error message "Multiple attributes of type 'Microsoft.VisualStudio.TestTools.UnitTesting.TestClassAttribute' found."

DuplicateTestMethodAttribute Test Asset

[TestClass]
public class TestClass1
{
    [TestMethod]
    [MyTestMethod]  // Duplicate TestMethod attribute - causes this test to fail
    public void Test1() { }

    [TestMethod]
    public void Test2() { }  // This test passes
}

public class MyTestMethodAttribute : TestMethodAttribute
{
    public MyTestMethodAttribute([CallerFilePath] string callerFilePath = "", [CallerLineNumber] int callerLineNumber = -1)
        : base(callerFilePath, callerLineNumber) { }
}

DuplicateTestClassAttribute Test Asset

[TestClass]
[MyTestClass]  // Duplicate TestClass attribute - causes discovery failure
public class TestClass2
{
    [TestMethod]
    public void Test1() { }
}

public class MyTestClassAttribute : TestClassAttribute { }

The tests validate that duplicate attributes are properly detected and reported, ensuring appropriate error handling for both duplicate TestMethod and TestClass attribute scenarios.

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[Copilot]

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[Youssef1313]

@copilot

• Rename this test to DuplicateTestClassAttribute_ShouldFail
• Assert exit code is not success.
• Assert output contains "Multiple attributes of type 'Microsoft.VisualStudio.TestTools.UnitTesting.TestClassAttribute' found."

[Copilot]

Updated in commit 8f4cfd8:

• Renamed test to DuplicateTestClassAttribute_ShouldFail
• Changed assertion to AssertExitCodeIsNot(ExitCodes.Success)
• Added assertion for error message: "Multiple attributes of type 'Microsoft.VisualStudio.TestTools.UnitTesting.TestClassAttribute' found."

[Youssef1313]

@copilot

• Rename this test to DuplicateTestMethodAttribute_ShouldFail
• Assert exit code is AtLeastOneTestFailed, and assert that one test passes and one failed.

In addition, use two different test assets for the two tests.

[Copilot]

Updated in commit 0a42af8:

• Renamed first test to DuplicateTestMethodAttribute_ShouldFail
• Changed assertion to AssertExitCodeIs(ExitCodes.AtLeastOneTestFailed)
• Added assertion for summary: 1 passed, 1 failed
• Created two separate test assets:
  • DuplicateTestMethodAttribute for testing duplicate TestMethod attributes
  • DuplicateTestClassAttribute for testing duplicate TestClass attributes