Managing Global Setup and Teardown in Jest

When working with Jest, one of the most powerful features that often goes underutilized is global setup and teardown. Let me share some battle-tested strategies I’ve learned while managing test environments at scale.

Understanding Global Setup and Teardown

Think of global setup and teardown as your test suite’s morning routine and evening cleanup. Before running any tests, you might need to initialize a database, set up environment variables, or prepare shared resources. After all tests complete, you’ll want to clean everything up properly.

Implementing Global Setup

The most straightforward way to implement global setup is through globalSetup in your Jest configuration. Here’s how I typically structure it:

module.exports = {
  globalSetup: './setup.js',
  globalTeardown: './teardown.js'
};

module.exports = async () => {
  // Your setup logic here
  await initializeTestDatabase();
  process.env.TEST_API_KEY = 'test-key';
};

Best Practices for Global Setup

One lesson I’ve learned the hard way: keep your global setup focused and minimal. Here’s what I recommend:

1. Initialize shared resources that are truly global
2. Set up environment variables
3. Create necessary directory structures
4. Prepare test data that’s used across multiple test suites

Global Teardown: The Cleanup Crew

Your teardown should be like a good camping rule: leave no trace. Here’s how I structure my teardown:

module.exports = async () => {
  await cleanupTestDatabase();
  await removeTestFiles();
  // Reset any global state
  delete process.env.TEST_API_KEY;
};

Advanced Patterns

Something I’ve found incredibly useful is combining global setup with per-file setup when needed:

// In specific test files
beforeAll(async () => {
  // File-specific setup
  await setupTestSpecificData();
});

afterAll(async () => {
  // File-specific cleanup
  await cleanupTestSpecificData();
});

Tips and Gotchas

• Remember that global setup runs before all tests, so keep it lightweight
• Use environment variables for configuration that needs to be accessible everywhere
• Watch out for side effects that might affect other tests
• Consider using separate databases for different test suites if needed

Remember, good test setup is like a well-oiled machine - it should be reliable, predictable, and maintainable. By following these patterns, you’ll create a robust foundation for your test suite that scales with your project.