Split TestMethodRunner.cs into focused partial-class files

[Evangelink]

Overview

Fixes #9711.

TestMethodRunner.cs had grown to 591 lines and was the only class in src/Adapter/MSTestAdapter.PlatformServices/Execution/ not following the ClassName.Responsibility.cs partial-class split pattern used by its neighbors (TestMethodInfo, TestExecutionManager, TypeCache, TestClassInfo, UnitTestRunner).

Changes

Split into four focused partial-class files:

File	Lines	Responsibility
TestMethodRunner.cs	266	Fields, constructor, ExecuteAsync, RunTestMethodAsync, IsDataDrivenTest, GetAggregateOutcome — entry points & routing
TestMethodRunner.DataSource.cs	177	DataSourceAttribute-based data-driven tests
TestMethodRunner.DataRow.cs	107	Folded / DynamicData-style (ITestDataSource) data-driven tests
TestMethodRunner.Execution.cs	89	Core single-test execution (ExecuteTestAsync, UpdateResultsWithParentInfo)

This is a pure structural refactor — no logic changes. Method bodies were moved verbatim; the class is marked partial; usings were trimmed per-file.

GetAggregateOutcome was kept in the entry-point file since it's used by the routing logic in RunTestMethodAsync.

Acceptance criteria

• Split into 4 partial-class files following the ClassName.Responsibility.cs convention
• Each new file is under 300 lines
• Build succeeds (0 warnings, 0 errors across all target frameworks)
• All 898 MSTestAdapter.PlatformServices.UnitTests pass
• No behavioral changes — pure structural refactor

[Copilot]

Pull request overview

Refactors TestMethodRunner in MSTestAdapter.PlatformServices to match the existing ClassName.Responsibility.cs partial-class organization used by other classes in Execution/, improving navigability without changing behavior.

Changes:

• Converted TestMethodRunner to a partial type and retained entry-point/routing logic in TestMethodRunner.cs.
• Extracted data-driven execution paths into dedicated partial files (.DataSource.cs and .DataRow.cs).
• Moved core single-test execution helpers into TestMethodRunner.Execution.cs.

Show a summary per file

File	Description
src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodRunner.cs	Marks the type partial and keeps the primary entry points/routing plus aggregate outcome logic.
src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodRunner.DataSource.cs	Contains DataSourceAttribute-based data-driven execution logic.
src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodRunner.DataRow.cs	Contains folded / ITestDataSource (DynamicData-style) execution logic.
src/Adapter/MSTestAdapter.PlatformServices/Execution/TestMethodRunner.Execution.cs	Contains core single-test execution (ExecuteTestAsync) and result parent/execution id updates.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 0
• Review effort level: Low

[github-actions]

Note

🤖 Automated review by GitHub Copilot. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

Review Summary

Clean structural refactor — no issues found. All 22 review dimensions assessed.

Verification

Check	Result
All original methods accounted for	✅ 11/11 methods preserved with identical signatures
File naming convention	✅ Follows established ClassName.Responsibility.cs pattern (matches TestMethodInfo, TestExecutionManager, TypeCache, etc.)
using directives per file	✅ Properly trimmed — each partial imports only what it needs
Removed using from main file	✅ Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices correctly removed — no longer directly referenced
partial keyword	✅ Applied to class declaration in all 4 files
CI build (Linux Release)	✅ Passed

Dimension Assessment

#	Dimension	Verdict
1	Algorithmic Correctness	N/A — no logic changes
2	Threading & Concurrency	N/A — ConfigureAwait(false) patterns preserved verbatim
3	Security & IPC	N/A
4	Public API	N/A — class is internal sealed
5	Performance	N/A — zero runtime impact
6	Cross-TFM	N/A — no TFM-specific changes
7	Resource & IDisposable	N/A — dispose patterns preserved
8	Defensive Coding	N/A
9	Localization	N/A
10	Test Isolation	N/A — no test files
11	Assertion Quality	N/A
12	Flakiness	N/A
13	Test Completeness	N/A
14	Data-Driven Coverage	N/A
15	Code Structure	LGTM — this PR improves structure
16	Naming	LGTM — consistent with neighbors
17	Documentation	LGTM — XML doc summaries on each partial describe responsibility
18	Analyzer Quality	N/A
19	IPC Wire	N/A
20	Build Infrastructure	N/A
21	Scope & PR Discipline	LGTM — single concern, well-scoped
22	PowerShell	N/A

No blocking or major issues. Well-executed refactor that brings TestMethodRunner in line with the established partial-class conventions in its directory.