---

name: vscode-test-setup description: This skill provides comprehensive guidance for setting up and configuring test environments for VS Code extension projects. Use when initializing a new test infrastructure, configuring test runners (Mocha, Jest), setting up CI/CD test pipelines, integrating coverage tools (c8, nyc), or troubleshooting test configuration issues.

VS Code Extension Test Environment Setup

Overview

This skill enables rapid and reliable test environment setup for VS Code extension projects. It covers test framework configuration, CI/CD integration, coverage tooling, and best practices for maintainable test infrastructure.

When to Use This Skill

• Setting up test infrastructure for new VS Code extension projects
• Migrating from one test framework to another
• Configuring CI/CD pipelines for extension testing
• Setting up code coverage tools and thresholds
• Troubleshooting test configuration issues
• Optimizing test execution performance

Quick Start Setup

Step 1: Install Dependencies

# Core testing dependencies
npm install --save-dev \
  @vscode/test-cli \
  @vscode/test-electron \
  mocha \
  chai \
  sinon \
  sinon-chai \
  @types/mocha \
  @types/chai \
  @types/sinon

# Coverage tools
npm install --save-dev c8

# Optional: Additional assertions
npm install --save-dev chai-as-promised

Step 2: Create Test Configuration

Run the setup script to create all necessary configuration files:

# Execute from skill directory
python scripts/setup-test-env.py --project-path /path/to/extension

Or manually create the following files:

.vscode-test.js

const { defineConfig } = require('@vscode/test-cli');

module.exports = defineConfig({
  files: 'out/test/**/*.test.js',
  version: 'stable',
  workspaceFolder: './test-fixtures',
  launchArgs: [
    '--disable-extensions',
    '--disable-workspace-trust'
  ],
  mocha: {
    timeout: 20000,
    ui: 'bdd',
    color: true,
    retries: process.env.CI ? 2 : 0
  }
});

tsconfig.test.json

{
  "extends": "./tsconfig.json",
  "compilerOptions": {
    "module": "commonjs",
    "outDir": "./out/test",
    "rootDir": "./src",
    "types": ["mocha", "node", "chai", "sinon"]
  },
  "include": [
    "src/test/**/*.ts"
  ]
}

Step 3: Configure Package.json Scripts

{
  "scripts": {
    "compile": "tsc -p ./",
    "compile:test": "tsc -p ./tsconfig.test.json",
    "watch": "tsc -watch -p ./",
    "pretest": "npm run compile && npm run compile:test",
    "test": "vscode-test",
    "test:unit": "mocha out/test/unit/**/*.test.js --timeout 5000",
    "test:integration": "vscode-test",
    "test:coverage": "c8 npm run test:unit",
    "test:watch": "mocha out/test/unit/**/*.test.js --watch --timeout 5000",
    "tdd:red": "npm run test:unit -- --grep 'RED:'",
    "tdd:green": "npm run test:unit",
    "tdd:refactor": "npm run lint && npm run test:unit",
    "tdd:quality-gate": "npm run test:coverage && npm run lint"
  }
}

Step 4: Create Directory Structure

src/
├── test/
│   ├── unit/                    # Pure unit tests (no VS Code API)
│   │   ├── setup.ts             # Unit test setup
│   │   ├── utils.test.ts
│   │   └── models.test.ts
│   ├── integration/             # Tests requiring VS Code API
│   │   ├── setup.ts             # Integration test setup
│   │   ├── extension.test.ts
│   │   └── commands.test.ts
│   ├── e2e/                     # End-to-end tests
│   │   └── activation.test.ts
│   ├── fixtures/                # Test data
│   │   ├── sample-workspace/
│   │   └── test-data.json
│   └── helpers/                 # Shared test utilities
│       ├── vscode-mock.ts
│       ├── async-helpers.ts
│       └── test-utils.ts
test-fixtures/                   # VS Code test workspace
└── .vscode/
    └── settings.json

Test Framework Configuration

Mocha Configuration

.mocharc.json

{
  "require": ["ts-node/register"],
  "extension": ["ts"],
  "spec": "src/test/unit/**/*.test.ts",
  "timeout": 5000,
  "ui": "bdd",
  "color": true,
  "reporter": "spec",
  "exit": true
}

Unit Test Setup (src/test/unit/setup.ts)

import * as chai from 'chai';
import * as sinonChai from 'sinon-chai';

// Configure chai
chai.use(sinonChai);

// Configure chai-as-promised for async tests
import chaiAsPromised = require('chai-as-promised');
chai.use(chaiAsPromised);

export { expect } from 'chai';
export { default as sinon } from 'sinon';

Integration Test Setup (src/test/integration/setup.ts)

import * as path from 'path';
import * as Mocha from 'mocha';
import { glob } from 'glob';

export async function run(): Promise<void> {
  const mocha = new Mocha({
    ui: 'bdd',
    color: true,
    timeout: 20000,
    retries: process.env.CI ? 2 : 0
  });

  const testsRoot = path.resolve(__dirname, '.');
  const files = await glob('**/*.test.js', { cwd: testsRoot });

  files.forEach((f) => mocha.addFile(path.resolve(testsRoot, f)));

  return new Promise((resolve, reject) => {
    mocha.run((failures) => {
      if (failures > 0) {
        reject(new Error(`${failures} tests failed.`));
      } else {
        resolve();
      }
    });
  });
}

Jest Configuration (Alternative)

jest.config.js

/** @type {import('jest').Config} */
module.exports = {
  preset: 'ts-jest',
  testEnvironment: 'node',
  roots: ['<rootDir>/src/test/unit'],
  testMatch: ['**/*.test.ts'],
  moduleFileExtensions: ['ts', 'js', 'json'],
  collectCoverageFrom: [
    'src/**/*.ts',
    '!src/test/**',
    '!**/*.d.ts'
  ],
  coverageDirectory: 'coverage',
  coverageReporters: ['text', 'lcov', 'html'],
  coverageThreshold: {
    global: {
      branches: 80,
      functions: 80,
      lines: 80,
      statements: 80
    }
  },
  setupFilesAfterEnv: ['<rootDir>/src/test/unit/setup.ts'],
  moduleNameMapper: {
    '^vscode$': '<rootDir>/src/test/helpers/vscode-mock.ts'
  }
};

Coverage Configuration

c8 Configuration

package.json

{
  "c8": {
    "include": ["src/**/*.ts"],
    "exclude": [
      "src/test/**",
      "**/*.d.ts",
      "**/node_modules/**"
    ],
    "reporter": ["text", "html", "lcov"],
    "all": true,
    "clean": true,
    "check-coverage": true,
    "branches": 80,
    "functions": 80,
    "lines": 80,
    "statements": 80,
    "report-dir": "./coverage"
  }
}

NYC Configuration (Alternative)

.nycrc.json

{
  "extends": "@istanbuljs/nyc-config-typescript",
  "include": ["src/**/*.ts"],
  "exclude": ["src/test/**", "**/*.d.ts"],
  "reporter": ["text", "html", "lcov"],
  "all": true,
  "check-coverage": true,
  "branches": 80,
  "functions": 80,
  "lines": 80,
  "statements": 80
}

CI/CD Configuration

GitHub Actions

.github/workflows/test.yml

name: Test

on:
  push:
    branches: [main, develop]
  pull_request:
    branches: [main]

jobs:
  test:
    strategy:
      matrix:
        os: [ubuntu-latest, windows-latest, macos-latest]
        vscode-version: ['stable', 'insiders']
      fail-fast: false

    runs-on: ${{ matrix.os }}

    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'

      - name: Install dependencies
        run: npm ci

      - name: Compile
        run: npm run compile

      - name: Run unit tests
        run: npm run test:unit

      - name: Run integration tests (Linux)
        if: runner.os == 'Linux'
        run: xvfb-run -a npm run test:integration
        env:
          VSCODE_TEST_VERSION: ${{ matrix.vscode-version }}

      - name: Run integration tests (Windows/macOS)
        if: runner.os != 'Linux'
        run: npm run test:integration
        env:
          VSCODE_TEST_VERSION: ${{ matrix.vscode-version }}

      - name: Upload coverage
        if: matrix.os == 'ubuntu-latest' && matrix.vscode-version == 'stable'
        uses: codecov/codecov-action@v4
        with:
          file: ./coverage/lcov.info
          fail_ci_if_error: true

  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'
      - run: npm ci
      - run: npm run lint

TDD Quality Gate Workflow

.github/workflows/tdd-quality.yml

name: TDD Quality Gate

on:
  push:
    branches: [main]
  pull_request:

jobs:
  tdd-check:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'

      - name: Install dependencies
        run: npm ci

      - name: Compile
        run: npm run compile

      - name: Run TDD Quality Gate
        run: npm run tdd:quality-gate

      - name: Check coverage thresholds
        run: npx c8 check-coverage

      - name: Generate coverage report
        run: npx c8 report --reporter=text

      - name: Upload coverage report
        uses: actions/upload-artifact@v4
        with:
          name: coverage-report
          path: coverage/

VS Code Launch Configuration

.vscode/launch.json

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Run Extension",
      "type": "extensionHost",
      "request": "launch",
      "args": [
        "--extensionDevelopmentPath=${workspaceFolder}"
      ],
      "outFiles": ["${workspaceFolder}/out/**/*.js"],
      "preLaunchTask": "npm: compile"
    },
    {
      "name": "Run Integration Tests",
      "type": "extensionHost",
      "request": "launch",
      "args": [
        "--extensionDevelopmentPath=${workspaceFolder}",
        "--extensionTestsPath=${workspaceFolder}/out/test/integration"
      ],
      "outFiles": ["${workspaceFolder}/out/**/*.js"],
      "preLaunchTask": "npm: compile"
    },
    {
      "name": "Run Unit Tests",
      "type": "node",
      "request": "launch",
      "program": "${workspaceFolder}/node_modules/mocha/bin/_mocha",
      "args": [
        "--timeout",
        "5000",
        "out/test/unit/**/*.test.js"
      ],
      "console": "integratedTerminal",
      "internalConsoleOptions": "neverOpen",
      "preLaunchTask": "npm: compile"
    },
    {
      "name": "Debug Current Test File",
      "type": "node",
      "request": "launch",
      "program": "${workspaceFolder}/node_modules/mocha/bin/_mocha",
      "args": [
        "--timeout",
        "999999",
        "--grep",
        "",
        "${file}"
      ],
      "console": "integratedTerminal",
      "internalConsoleOptions": "neverOpen",
      "preLaunchTask": "npm: compile"
    }
  ]
}

.vscode/tasks.json

{
  "version": "2.0.0",
  "tasks": [
    {
      "type": "npm",
      "script": "compile",
      "problemMatcher": "$tsc",
      "group": "build",
      "label": "npm: compile"
    },
    {
      "type": "npm",
      "script": "watch",
      "problemMatcher": "$tsc-watch",
      "isBackground": true,
      "group": "build",
      "label": "npm: watch"
    },
    {
      "type": "npm",
      "script": "test:unit",
      "problemMatcher": [],
      "group": "test",
      "label": "npm: test:unit"
    },
    {
      "type": "npm",
      "script": "test:coverage",
      "problemMatcher": [],
      "group": "test",
      "label": "npm: test:coverage"
    }
  ]
}

Test Fixtures Setup

test-fixtures/.vscode/settings.json

{
  "editor.formatOnSave": false,
  "editor.tabSize": 2,
  "files.autoSave": "off",
  "terminal.integrated.defaultProfile.linux": "bash",
  "terminal.integrated.defaultProfile.osx": "zsh",
  "terminal.integrated.defaultProfile.windows": "PowerShell"
}

Test Data Factory

// src/test/helpers/test-data-factory.ts
import * as vscode from 'vscode';

export class TestDataFactory {
  static createTerminalOptions(
    overrides: Partial<vscode.TerminalOptions> = {}
  ): vscode.TerminalOptions {
    return {
      name: 'Test Terminal',
      cwd: '/tmp',
      env: { TEST_ENV: 'true' },
      ...overrides
    };
  }

  static createWebviewContent(title: string): string {
    return `<!DOCTYPE html>
    <html>
    <head><title>${title}</title></head>
    <body><h1>Test Content</h1></body>
    </html>`;
  }

  static createMockTerminalState(): any {
    return {
      id: 1,
      name: 'Terminal 1',
      processState: 'running',
      scrollback: 'mock scrollback content',
      cwd: '/home/user'
    };
  }

  static createMockSessionData(): any {
    return {
      version: 1,
      terminals: [this.createMockTerminalState()],
      savedAt: Date.now()
    };
  }
}

Troubleshooting Common Issues

Issue: Tests timeout in CI

Symptoms: Tests pass locally but timeout in GitHub Actions

Solutions:

1. Use xvfb-run for Linux headless testing
2. Increase timeout in mocha config
3. Add retries for flaky tests

# GitHub Actions
- name: Run tests (Linux)
  if: runner.os == 'Linux'
  run: xvfb-run -a npm run test:integration

Issue: ES Module import errors

Symptoms: ERR_REQUIRE_ESM when importing chai or other modules

Solutions:

1. Use dynamic imports for ESM modules
2. Pin package versions to CommonJS-compatible versions

// Use dynamic import
const chai = await import('chai');
const { expect } = chai;

Issue: VS Code API not available in unit tests

Symptoms: Cannot find module 'vscode'

Solutions:

1. Separate unit tests from integration tests
2. Use VS Code API mocks for unit tests

// jest.config.js
moduleNameMapper: {
  '^vscode$': '<rootDir>/src/test/helpers/vscode-mock.ts'
}

Issue: Coverage not tracking TypeScript files

Symptoms: Coverage shows 0% or missing files

Solutions:

1. Configure source maps correctly
2. Use proper include/exclude patterns

{
  "compilerOptions": {
    "sourceMap": true,
    "inlineSources": true
  }
}

Issue: Flaky tests due to async timing

Symptoms: Tests fail intermittently

Solutions:

1. Use proper async/await
2. Add explicit waits for async operations
3. Avoid time-dependent assertions

// Bad
setTimeout(() => expect(value).to.equal(1), 100);

// Good
await waitForCondition(() => value === 1);
expect(value).to.equal(1);

Resources

For detailed reference documentation, see:

• references/framework-comparison.md - Mocha vs Jest comparison
• references/ci-templates.md - CI/CD pipeline templates
• scripts/setup-test-env.py - Automated environment setup