[dotnet test] Extend --list-tests command to respect filters and provide machine‑readable output

[thomasdgx]

Problem

The current dotnet test --list-tests command lists all tests in a project, but it does not respect filters (e.g., --filter Category=Integration). This makes it difficult to preview which tests would actually be selected before execution. Developers often need to validate filter expressions without running the tests.

Proposal

Enhance the existing --list-tests command with the following capabilities:

• Apply all existing filters (--filter, runsettings, traits, etc.).
• Output only the matching test cases.
• Support machine‑readable formats (e.g., JSON or XML) for CI/CD integration.

Example Usage

dotnet test --filter Category=Integration --list-tests --output-format json

Benefits

• Quickly validate filter expressions without executing tests.
• Save time in large test suites.
• Enable CI/CD workflows to check test selection logic programmatically.
• Provide consistent behavior with vstest.console.exe --list-tests, but integrated into dotnet test.

Use Case

In a CI/CD environment, I need to determine whether a given test assembly contains any tests that match the specified filters (e.g., --filter Category=Integration).

• If no tests match, the pipeline should skip executing that assembly, saving time and resources.
• If tests do match, the pipeline should forward the assembly for execution.

This requires a way to run dotnet test --list-tests with filters applied, producing a machine‑readable output that can be consumed by the CI/CD pipeline.