Implement PytestSubprocessInstance

TEST_IMPLEMENTATION_SUMMARY.md

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+# Test Implementation Summary for PytestSubprocessInstance
+
+## Overview
+
+This document summarizes the comprehensive test implementation for the `PytestSubprocessInstance` refactor PR.
+
+## Files Created/Modified
+
+### 1. New Test File: `pytestSubprocessInstance.unit.test.ts`
+**Location:** `src/test/testing/testController/pytest/pytestSubprocessInstance.unit.test.ts`
+
+**Test Coverage:** 31 unit tests covering:
+
+#### Initialization (4 tests)
+- Constructor initializes properties correctly
+- Initialize creates test IDs file
+- Initialize handles empty test IDs
+- Initialize propagates errors from writeTestIdsFile
+
+#### Process Management (2 tests)
+- setProcess stores process reference
+- setProcess can be called multiple times
+
+#### Cancellation Handling (6 tests)
+- setCancellationToken stores token reference
+- isCancelled returns false when no token set
+- isCancelled returns false when token is not cancelled
+- isCancelled returns true when token is cancelled
+- isCancelled reflects token state changes
+- handleDataReceivedEvent skips processing when cancelled
+
+#### Data Handling (5 tests)
+- handleDataReceivedEvent resolves deferred on success status
+- handleDataReceivedEvent resolves deferred on error status
+- handleDataReceivedEvent does not resolve on unknown status
+- getExecutionPromise returns the same promise on multiple calls
+- handleDataReceivedEvent resolves promise only once
+
+#### Cleanup and Disposal (6 tests)
+- dispose kills process if running
+- dispose completes successfully when test IDs file exists
+- dispose handles missing process gracefully
+- dispose handles missing test IDs file gracefully
+- dispose handles process kill error gracefully
+- dispose performs cleanup operations
+
+#### Integration Scenarios (3 tests)
+- Full lifecycle: initialize, set process, receive data, dispose
+- Cancellation during execution prevents data processing
+- Multiple instances can coexist independently
+
+#### Debug Mode (1 test)
+- Debug mode flag is stored correctly
+
+#### Edge Cases (4 tests)
+- Dispose before initialize does not throw
+- Initialize can be called before setting process
+- Data can be received before process is set
+- Cancellation token can be set multiple times
+
+**Status:** ✅ All 31 tests passing
+
+### 2. Enhanced Test File: `pytestExecutionAdapter.unit.test.ts`
+**Location:** `src/test/testing/testController/pytest/pytestExecutionAdapter.unit.test.ts`
+
+**New Test Suites Added:**
+
+#### Environment Extension Integration (6 tests)
+- Uses environment extension when enabled
+- Handles cancellation with environment extension
+- Handles environment not found gracefully
+- Environment extension passes correct environment variables
+- Environment extension handles process exit with non-zero code
+
+#### Cancellation and Cleanup (4 tests)
+- Cancellation triggers process kill in legacy mode
+- Instance cleanup happens after process close
+- Promise resolution happens correctly on success
+- Promise resolution happens correctly on error
+
+**Key Features Tested:**
+- ✅ useEnvExtension() path coverage
+- ✅ Cancellation behavior in both env extension and legacy modes
+- ✅ Cleanup and disposal lifecycle
+- ✅ Promise resolution guarantees
+- ✅ Process kill on cancellation
+- ✅ Environment variable passing
+- ✅ Error handling
+
+## Test Strategy
+
+### Unit Testing Approach
+- **Isolation:** All external dependencies mocked via sinon stubs
+- **Mock Strategy:** Minimal mocks with only required methods
+- **Type Safety:** Proper TypeScript typing for all test payloads
+- **Error Handling:** Graceful handling of edge cases and errors
+
+### Integration Testing
+- **Environment Extension Path:** Tests verify correct integration with the new environment extension API
+- **Legacy Path:** Tests ensure backward compatibility with execObservable
+- **Cancellation:** Comprehensive testing of cancellation token handling and cleanup
+- **Promise Resolution:** Verification that promises resolve correctly in all scenarios
+
+### Coverage Areas
+
+#### 1. Initialization & Setup
+- Subprocess instance creation
+- Test IDs file creation
+- Process attachment
+- Cancellation token setup
+
+#### 2. Execution Flow
+- Environment extension vs legacy execution paths
+- Environment variable configuration
+- Process spawning
+- Output handling
+
+#### 3. Cancellation
+- Token propagation
+- Process kill on cancellation
+- Cleanup after cancellation
+- Promise resolution on cancellation
+
+#### 4. Cleanup & Disposal
+- Process kill
+- File cleanup
+- Instance removal from active instances map
+- Error handling during cleanup
+
+#### 5. Error Scenarios
+- Missing environment
+- Process kill failures
+- File deletion failures
+- Non-zero exit codes
+
+## Running the Tests
+
+```bash
+# Run all PytestSubprocessInstance tests
+npm run test:unittests -- --grep "PytestSubprocessInstance"
+
+# Run environment extension integration tests
+npm run test:unittests -- --grep "Environment Extension Integration"
+
+# Run cancellation tests
+npm run test:unittests -- --grep "Cancellation"
+
+# Run all pytest execution adapter tests
+npm run test:unittests -- --grep "pytest test execution adapter"
+```
+
+## Key Testing Insights
+
+### 1. Cancellation Testing
+Tests verify that:
+- Cancellation tokens are properly propagated
+- Processes are killed when cancelled
+- Data processing stops when cancelled
+- Promises resolve correctly after cancellation
+- Cleanup happens even when cancelled
+
+### 2. Environment Extension Path
+Tests ensure:
+- `useEnvExtension()` determines the execution path
+- `getEnvironment()` is called correctly
+- `runInBackground()` receives proper arguments
+- Environment variables are passed correctly
+- Process events (onExit) are handled properly
+
+### 3. Promise Resolution
+Tests guarantee:
+- Execution promises resolve on success
+- Execution promises resolve on error
+- Promises don't hang on cancellation
+- Cleanup happens before promise resolution
+- Multiple calls return the same promise
+
+### 4. Resource Cleanup
+Tests verify:
+- Processes are killed on disposal
+- Test IDs files are deleted
+- Instances are removed from tracking map
+- Errors during cleanup don't throw
+- Cleanup works in all scenarios
+
+## Future Enhancements
+
+Consider adding:
+1. **Performance tests** for subprocess overhead
+2. **Stress tests** for multiple concurrent instances
+3. **Integration tests** with real pytest processes
+4. **Memory leak tests** for long-running scenarios
+
+## Conclusion
+
+The test implementation provides comprehensive coverage of:
+- ✅ Core functionality (initialization, execution, disposal)
+- ✅ useEnvExtension path
+- ✅ Cancellation behavior
+- ✅ Cleanup and promise resolution
+- ✅ Error handling and edge cases
+
+All tests follow the repository's testing patterns and conventions, using proper mocking strategies and maintaining type safety throughout.