Add analyzer and code fix for test methods with out/ref parameters

[Copilot]

Test methods with out or ref parameters are not properly supported by the test framework. This PR adds a new informational analyzer with automatic code fix and runtime warning to help users identify and migrate away from this pattern before support is dropped in a future major version.

Example code that triggers the warning:

[TestMethod]
[DataRow("Hello", "World")]
public void TestMethod1(out string s, ref string s2)  // ℹ️ MSTEST0060 info diagnostic
{
    s = "";
}

Changes Made

New Analyzer (MSTEST0060)

• Created: AvoidOutRefTestMethodParametersAnalyzer as a separate analyzer
• Severity: Info (informational suggestion, not warning)
• Category: Usage
• Message: "Test method '{0}' has 'out' or 'ref' parameters for which support will be dropped in a future major version"
• Description: "'out' and 'ref' parameters add no value in test methods and they can safely be replaced by normal parameters."
• Supports: All attributes inheriting from [TestMethod] (e.g., [DataTestMethod])

Code Fix

• Created: AvoidOutRefTestMethodParametersFixer
• Action: Automatically removes out and ref modifiers from test method parameters
• Title: "Remove 'out' and 'ref' modifiers"
• Implementation: Simplified to directly find the method declaration using FindNode and always apply changes (no unnecessary checks)
• Supports: Batch fixing via FixAllProvider

Runtime Warning

• Modified: TestMethodValidator.IsValidTestMethod to detect out/ref parameters during test discovery/validation
• Behavior: Method returns true (non-blocking) but adds warning to the warnings collection
• Message: Uses Resource.UTA_OutRefParametersNotSupported for consistency across compile-time and runtime
• Optimization: Checks parameters.Length > 0 before LINQ enumeration to avoid unnecessary overhead

Localization

• Added 3 resource strings in analyzer Resources.resx
• Added 1 resource string in code fix CodeFixResources.resx
• Added 1 resource string in runtime Resource.resx
• Note: xlf files are auto-generated during build and have been updated with correct indentation

Tests

• Updated AvoidOutRefTestMethodParametersAnalyzerTests.cs with code fix verification
• Added test for [DataTestMethod] attribute to verify inheritance detection
• 6 comprehensive test cases covering: out parameters, ref parameters, both together, normal parameters, non-test methods, and inherited test method attributes
• Tests verify both diagnostic detection and code fix application

Migration Path

This approach provides a gradual, non-breaking migration path with automatic fix capability:

1. Now: Users receive informational warnings at compile-time and during test discovery, with one-click code fix available
2. Later: Can upgrade to stricter enforcement (blocking) in a future major version

Not a breaking change: Existing tests with out/ref parameters continue to run, but users are warned about the pattern during validation and can automatically fix it.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Disallow test methods with out/ref parameters</issue_title>
<issue_description>Today, the following is allowed:

        [TestMethod]
        [DataRow("Hello", "World")]
        public void TestMethod1(out string s, ref string s2)
        {
            s = "";
        }

I think we should:

1. Fail at run time when we encounter such a test method.
2. Update the analyzer for test method validity to also produce a compile-time warning.

It's technically a breaking change, but I think it's acceptable and is unlikely that people are doing this today.</issue_description>

<agent_instructions>Create a new analyzer for this and also emit a warning inside of the handling of MSTest</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@Evangelink If we want to be really safe, we could start by introducing the analyzer and wait for a few versions.

• Fixes Disallow test methods with out/ref parameters #7058

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[Evangelink]

@copilot please create a different analyzer as current analyzer severity is set to "warning" and so is more tuned for cases that really cause problem at runtime. This case is more of a suggestion so we can be stricter on next breaking change.

You should also change the implementation on MSTest to not fail but just report a warning.

[Copilot]

@copilot please create a different analyzer as current analyzer severity is set to "warning" and so is more tuned for cases that really cause problem at runtime. This case is more of a suggestion so w...

I've updated the implementation based on your feedback:

1. Created new analyzer (MSTEST0060) - AvoidOutRefTestMethodParametersAnalyzer with Info severity instead of modifying existing MSTEST0003
2. Changed runtime behavior - Now logs a warning via TestContext.WriteLine instead of failing the test
3. Reverted all changes to existing TestMethodShouldBeValidAnalyzer and HasCorrectTestMethodSignature

See commits:

• dcc5dc1 - Code review fixes (category change, resource extraction)
• 8b1a5b7 - Main implementation with new analyzer and runtime warning

The gradual approach allows users to see warnings now and prepare for stricter enforcement in future versions.

[Evangelink]

@copilot let's add a codefix that removes the out or/and ref part. The xlf files are auto-generated as part of the build so don't process them manually.

[Copilot]

@copilot let's add a codefix that removes the out or/and ref part. The xlf files are auto-generated as part of the build so don't process them manually.

Added code fix in commit 9a75cb2. The AvoidOutRefTestMethodParametersFixer removes out and ref modifiers from test method parameters. Xlf files will be auto-generated during build as you mentioned.

[Evangelink]

@copilot please fix the indentation of the first <trans-unit section you have added to all .xlf in this PR