Add test coverage for ResultsComparer and CLI helper paths

[LoopedBard3]

Summary

This expands automated coverage in the repo’s tooling-focused test surface without large production refactors.

What changed

• Added a new ResultsComparer.Tests project covering:

  • file and directory input handling
  • JSON deserialization from file/stream
  • stats aggregation and output behavior
  • zip/tar.gz decompression flows
  • duplicate-result/version-selection behavior
  • CLI paths for invalid thresholds, missing inputs, and matrix output

• Expanded BenchmarkDotNet.Extensions command-line option tests to cover:

  • string parameter parsing
  • boolean switch parsing
  • missing/invalid integer argument paths
  • absent-switch behavior

• Improved Startup.Tests reliability by skipping ETW-dependent Windows tests when not running elevated, instead of aborting the run

Small correctness fixes found while adding coverage

The new tests exposed a few edge-case bugs, which are fixed in this PR:

• CommandLineOptions.ParseAndRemoveStringsParameter now handles missing switches safely
• ResultsComparer.Program now tolerates a missing optional --filter
• TwoInputsComparer now treats EquivalenceTestConclusion.Base as a no-diff case
• ResultsComparer.Data moniker parsing is now null-safe for additional archive path shapes

Validation

Validated the affected suites in the available environment:

• ResultsComparer.Tests passing
• targeted BenchmarkDotNet.Extensions command-line tests passing
• Startup.Tests now skip environment-dependent cases cleanly

Note: test projects are kept at net11.0; full execution of those targets requires a local/CI environment with the .NET 11 SDK installed.

[Copilot]

Pull request overview

Adds new unit tests and small robustness tweaks across tooling to improve confidence in ResultsComparer output/CLI parsing and reduce platform-specific test failures.

Changes:

• Added a new ResultsComparer.Tests project with coverage for Program, Data, Helper, and Stats.
• Updated ResultsComparer logic for filter handling, moniker parsing, and equivalence-test conclusions.
• Improved platform gating in Startup.Tests and strengthened/nullability-corrected tests in the BenchmarkDotNet.Extensions harness.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/tools/ScenarioMeasurement/Startup.Tests/StartupTests.cs	Updates Windows/Linux platform detection and adds an admin-privilege gate for ETW-related tests.
src/tools/ResultsComparer/TwoInputsComparer.cs	Treats EquivalenceTestConclusion.Base as non-difference (like Same) when filtering results.
src/tools/ResultsComparer/ResultsComparer.sln	Adds the new ResultsComparer.Tests project and additional solution configurations.
src/tools/ResultsComparer/Properties/AssemblyInfo.cs	Exposes internals to ResultsComparer.Tests via InternalsVisibleTo.
src/tools/ResultsComparer/Program.cs	Makes filter parsing resilient to null filter arrays.
src/tools/ResultsComparer/Data.cs	Adjusts moniker detection (including empty-key guard and Contains-based matching for newer TFMs).
src/tools/ResultsComparer.Tests/StatsTests.cs	Adds unit tests for Stats formatting/aggregation and validation behavior.
src/tools/ResultsComparer.Tests/ResultsComparerTestData.cs	Adds a JSON test-data generator for BDN-like inputs.
src/tools/ResultsComparer.Tests/ResultsComparer.Tests.csproj	Introduces the new ResultsComparer unit test project.
src/tools/ResultsComparer.Tests/ProgramTests.cs	Adds CLI-level tests validating error output and “no diffs” behavior.
src/tools/ResultsComparer.Tests/HelperTests.cs	Adds tests for file discovery and JSON deserialization helpers.
src/tools/ResultsComparer.Tests/DataTests.cs	Adds tests for nested zip + tar.gz extraction and dedup/version preference logic.
src/tests/harness/BenchmarkDotNet.Extensions.Tests/PartitionFilterTests.cs	Makes parsed config nullable-aware and asserts non-null on success.
src/tests/harness/BenchmarkDotNet.Extensions.Tests/CommandLineOptionsTests.cs	Adds more test cases for parsing/removal helpers (strings/bool/int).
src/harness/BenchmarkDotNet.Extensions/CommandLineOptions.cs	Fixes parsing when the target string parameter switch is missing.

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[Copilot]

Pull request overview

Copilot reviewed 18 out of 18 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated no new comments.

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[Copilot]

Pull request overview

Copilot reviewed 19 out of 19 changed files in this pull request and generated no new comments.

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[Copilot]

Pull request overview

Copilot reviewed 22 out of 22 changed files in this pull request and generated 1 comment.

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[Copilot]

In CreateTarGzArchive, each TarEntry's DataStream is set to a new MemoryStream but never disposed. Even though this is test-only code, it’s easy to avoid leaking disposables by creating the MemoryStream in a using scope and disposing it after TarWriter.WriteEntry returns.

Suggested change

	var tarEntry = new UstarTarEntry(TarEntryType.RegularFile, entryName)
	{
	DataStream = new MemoryStream(Encoding.UTF8.GetBytes(content))
	using var dataStream = new MemoryStream(Encoding.UTF8.GetBytes(content));
	var tarEntry = new UstarTarEntry(TarEntryType.RegularFile, entryName)
	{
	DataStream = dataStream