Testing Guide

Test Strategy Overview

The CSS & JS Minifier extension uses VS Code’s extension testing framework with Mocha. The current test suite covers 171 tests (2 of them skipped) across six files, spanning activation, main functionality, new-file naming, file prefix validation, workspace capabilities, and internationalization. Both CSS and JS minification are fully local (LightningCSS + oxc-minify) so tests run fast with no network dependency or rate-limiting concerns.

Test Structure

Test Files (src/test/)

File Management & Test Isolation

Temporary File Strategy

Configuration tests use temporary files to avoid modifying source fixtures:

const sourceFile = path.join(__dirname, "..", "..", "src", "test", "fixtures", "test.css");
const testFile = path.join(__dirname, "fixtures", "temp-test.css");
fs.copyFileSync(sourceFile, testFile);

Comprehensive Cleanup Strategy

Each test suite includes cleanup in beforeAll hooks:

• Reset all configurations to defaults
• Remove generated minified files (.min, .compressed, etc.)
• Restore original fixture files from source

Sinon Spy Management

this.afterEach(function () {
  sinon.restore();
});

Running Tests

VS Code Tasks (Recommended)

Access via Ctrl/Cmd + Shift + P → “Tasks: Run Task”:

Command Line

# Complete test suite (compile + lint + all tests)
npm test

# Individual suites (grep-based)
npx vscode-test --grep "Configuration Test Suite"
npx vscode-test --grep "JS & CSS Minifier Test Suite"
npx vscode-test --grep "CSS nth-child Test Suite"
npx vscode-test --grep "Keybinding Test Suite"
npx vscode-test --grep "Virtual Workspace Test Suite"
npx vscode-test --grep "Internationalization"
npx vscode-test --grep "File Service Test Suite"
npx vscode-test --grep "File Prefix Validation"
npx vscode-test --grep "Activation Events"
npx vscode-test --grep "Runtime Localization"

# Specific test
npx vscode-test --grep "autoOpenNewFile setting - enabled"

# Under a specific display locale (VS Code Language Pack must be installed)
VSCODE_LOCALE=es npm test
VSCODE_LOCALE=fr npx vscode-test --grep "Internationalization"
VSCODE_LOCALE=qps-ploc npm test  # pseudo-locale, no pack needed

# Build only (no tests)
npm run pretest

# Coverage: per-file summary for src/** plus coverage/lcov.info
npm run test:coverage

See docs/INTERNATIONALIZATION.md#testing-under-a-specific-locale for the runtime localization test wiring.

Test coverage

npm run test:coverage is opt-in. npm test is unchanged and collects nothing.

npm run test:coverage

It runs pretest:coverage (compile tests, rebuild the bundle with webpack --env coverage, lint, copy fixtures), then vscode-test --coverage --coverage-output coverage, then scripts/coverage-report.mjs. The output is a per-file table of lines, functions and branches for src/** (without src/test/**) and coverage/lcov.info with repository-relative paths. There is no threshold: the numbers are for orientation.

How it is wired:

• .vscode-test.mjs holds a coverage block (include, exclude, reporter: ['lcovonly']). It is a sibling of tests inside defineConfig({ tests, coverage }); a flat defineConfig({ files, version, coverage }) ignores it silently. The CLI also ignores coverage.output, so the folder comes from --coverage-output in the npm script. Patterns are matched against absolute paths, which is why they start with **/.
• The extension under test runs from the webpack bundle dist/extension.js, not from the out/ files that tsc emits. Webpack’s default source-map paths (webpack://css-js-minifier/./src/...) point at nothing c8 can read, so it reports every file at a false 100% or 0%. --env coverage makes webpack.config.cjs set devtoolModuleFilenameTemplate to [absolute-resource-path], which maps the bundle back to the real src/** files. Regular builds and the shipped source maps never get these absolute paths.
• c8 also lists non-source modules of the bundle (external commonjs "vscode", webpack/bootstrap) as 100% covered. scripts/coverage-report.mjs drops them, rewrites lcov.info with only src/**, and prints the table.
• scripts/coverage-report.mjs exits 1 when src/extension.ts is missing from the lcov file. That means the bundle was built without --env coverage and only the few files the tests import from out/ were measured, so the run is refused instead of showing a tiny table that looks complete.
• With includeAll: false, a file nothing loads, such as a type-only module, does not appear.

What it cannot measure: the minification itself runs in the Rust bindings lightningcss and oxc-minify, so the percentages describe the VS Code orchestration around them.

CI: the Ubuntu job of .github/workflows/test-vscode-stable.yml (VS Code Stable) reruns the suite with npm run test:coverage and appends the table to $GITHUB_STEP_SUMMARY. Both steps use continue-on-error, so a coverage problem never changes a required check. The other jobs are unchanged.

Local note: on macOS, VS Code needs the user-data path under 103 characters for its IPC socket. In a deeply nested checkout (for example a git worktree) the run fails with listen EINVAL ... main.sock. Pass a short directory through launchArgs: ['--user-data-dir=/tmp/short'] in a local, uncommitted copy of the config.

Development Workflow

Feature Development:

1. Start watch mode: “tasks: watch-tests”
2. Run the relevant suite for your change (e.g. Test: Configuration Suite Only).
3. Run the full suite before commit: Test: Run All Tests.

Bug Fixing:

1. Identify failing suite via Test: Run All Tests.
2. Focus on the specific suite.
3. Target a single test via Test: Specific Test by Name.

Test Data Management

Expected Minification Results

// CSS (LightningCSS output)
const cssMinifiedContent = "p{color:red}";

// JavaScript (oxc-minify output)
const jsMinifiedContent = 'function test(){for(var e=`Hello, World!`,t=``,n=0;n<e.length;n++)t+=String.fromCharCode(e.charCodeAt(n)+1);return t}';

Test File Organization

src/test/
├── activation.test.ts     # Activation Events regression guard (#168)
├── extension.test.ts      # Main test suite (41 tests, 2 skipped)
├── filePrefix.test.ts     # minifiedNewFilePrefix validation, command and on-save paths (#259, 77 tests)
├── fileService.test.ts    # New-file naming + overwrite guard (#255, 18 tests)
├── i18n.test.ts           # Static + runtime i18n suites (23 tests)
├── workspaceCapabilities.test.ts # Virtual workspace + capabilities (7 tests)
└── fixtures/
    ├── test.css           # Basic CSS test file
    ├── test.js            # Basic JS test file
    ├── test-minified.js   # Expected JS minified output
    ├── nth-child-test.css # CSS nth-child test case
    ├── starting-style.css # CSS @starting-style test case
    ├── large.css          # Larger CSS file for size-reduction tests
    ├── empty.css          # Empty file test case
    ├── empty.js           # Empty file test case
    └── test.txt           # Unsupported file type

Debugging Test Failures

Common Issues

1. Configuration Test Failures

   • VS Code configuration updates are asynchronous — use small delays after .update().
   • Always use temporary files, never modify source fixtures.

2. File Path Issues

   • Ensure npm run copy-fixtures ran during pretest.
   • Check out/test/fixtures/ directory exists.

3. In-Place Modification Conflicts

   • Use unique temporary file names per test.
   • Comprehensive cleanup in beforeAll hooks.

4. Runtime i18n Assertions Silently Pass Under English

   • Runtime Localization tests use vscode.env.language to decide what to assert. Under the default English locale several assertions no-op. Run them under a non-English locale (VSCODE_LOCALE=es npm test) or the pseudo-locale (VSCODE_LOCALE=qps-ploc npm test) to exercise them properly.

Best Practices

1. Source Protection: Never modify files in src/test/fixtures/.
2. Temporary Files: Use unique prefixes (temp-test.css).
3. Complete Cleanup: Remove generated and temporary files after tests.
4. Fixture Restoration: Copy fresh content from source when needed.
5. Spy Management: Always restore Sinon spies to prevent interference.
6. Descriptive Names: Use clear functionality descriptions for test names.
7. Content Verification: Assert specific minified output, not just “changed”.

Last Updated: 2026-10-28 Extension Version: 1.3.4 Test Suite: 171 tests across 6 files (activation, main, file service, file prefix, workspace capabilities, i18n)