MCP Tool: `Tests / Run` — auto-handle script recompilation before tests

[IvanMurzak]

Goal

When the user runs Tests / Run, Unity-MCP should ensure Unity is in a compiled, ready state. If scripts changed (or a compile is pending), trigger/await compilation, then run tests. If no compile is needed, run tests immediately.

Acceptance Criteria

• Detect compilation necessity before starting tests:
  • scripts were modified since last successful compile, or
  • Unity reports compilation is pending/in progress, or
  • domain reload is required due to script changes.
• If compilation is required and not already running, trigger a recompile (Unity script compilation refresh).
• If compilation is running, wait until it completes.
• If compilation is not required, run tests immediately (no waiting).
• If compilation was triggered by this action, wait for completion, then run the requested test(s).
• If compilation fails, do not run tests and return a clear error result including:
  • compiler errors summary (first N lines) + “see Unity console for full log”
  • status = failed

Expected Flow

1. AI calls Tests / Run (optionally with filter / test name).
2. Tool checks Unity compilation state + whether scripts changed.
3. If needed → trigger compile (if not already running) → await compile completion.
4. If compile succeeded → run tests.
5. Return structured result: compilation step outcome + test run outcome.

Edge Cases

• Compilation is already in progress when command starts → just wait.
• Continuous recompile loops / repeated changes while waiting → debounce and wait for a “stable” successful compile before running tests.
• Entered Play Mode / is playing → decide behavior (block tests or stop play mode) and document it.

Implementation Notes (Unity-side)

• Use Unity’s compilation hooks/state (e.g., UnityEditor.Compilation.CompilationPipeline events + EditorApplication.isCompiling), and only proceed to tests when compilation is finished and successful.
• Ensure the tool is resilient to domain reloads (store pending “run tests after compile” intent somewhere that survives reload if needed).