MCP Debugger

# packages/adapter-javascript/tests/unit/config-transformer.edge.test.ts @source-hash: 05cd4b9e975baebc @generated: 2026-02-10T00:41:07Z ## Edge Case Unit Tests for Config Transformer This test file validates the fault tolerance and edge case handling of the `config-transformer.js` utility functions, specifically focusing on malformed JSON parsing scenarios that could occur in real-world environments. ### Test Target Functions - `isESMProject` - Determines if a project uses ES modules based on package.json/tsconfig.json - `hasTsConfigPaths` - Checks if TypeScript path mappings are configured - `determineOutFiles` - Returns file patterns for output detection - `setDefaultFileSystem` - Dependency injection for filesystem operations ### Mock Infrastructure - **MockFileSystem (L14-39)**: Test double implementing FileSystem interface with configurable behavior - `setExistsMock()` (L18-20): Controls which file paths appear to exist - `setReadFileMock()` (L22-24): Controls file content returned for specific paths - `existsSync()` (L26-31): Delegates to mock or returns false - `readFileSync()` (L33-38): Delegates to mock or returns empty string ### Test Setup - **beforeEach (L46-52)**: Initializes fresh MockFileSystem, injects it via `setDefaultFileSystem`, sets default behavior (no files exist) - **afterEach (L54-57)**: Restores NodeFileSystem to prevent test pollution - **Constants**: Uses `proj-edge` directory structure with `src` subdirectory ### Test Cases 1. **Malformed package.json (L59-68)**: Verifies `isESMProject` gracefully handles invalid JSON in program directory without throwing 2. **Malformed tsconfig.json for ESM detection (L70-78)**: Tests `isESMProject` resilience against corrupted tsconfig in project root 3. **Malformed tsconfig.json for paths (L80-88)**: Ensures `hasTsConfigPaths` fails safely on invalid JSON 4. **Default output patterns (L90-94)**: Validates `determineOutFiles` fallback behavior when no user configuration provided ### Key Testing Patterns - **Fault tolerance**: All tests verify functions return false/defaults instead of throwing on malformed JSON - **Path-specific mocking**: Uses exact path matching to simulate realistic file system states - **Extension awareness**: Uses `.js` extensions to avoid forcing ESM detection through file extensions