Global Teardown with Jest

You're tasked with ensuring your Jest test suite cleans up after itself comprehensively. Sometimes, tests might leave behind resources like temporary files, database connections, or running services. Jest provides hooks for setting up and tearing down resources globally across all your tests. This challenge focuses on implementing a global teardown function to execute cleanup logic once all tests have completed.

Problem Description

Your goal is to implement a global teardown function in Jest for a TypeScript project. This function should be executed after all tests in your suite have finished running, regardless of whether they passed or failed. The purpose of this function is to clean up any resources that were initialized or used by the entire test suite.

Key Requirements:

• Global Teardown: Implement a teardown function that Jest will execute once.
• TypeScript Compatibility: The solution must be written in TypeScript.
• Jest Configuration: You'll need to configure Jest to recognize and use your global teardown file.
• Asynchronous Operations: The teardown function should be able to handle asynchronous cleanup operations.

Expected Behavior:

When Jest runs your test suite, the teardown function defined in your global teardown file should be invoked exactly once, after the very last test has finished. This function should have access to any necessary context or be able to perform its cleanup operations independently.

Edge Cases:

• Tests Failures: The teardown function must execute even if some or all tests fail.
• No Tests Found: The teardown function should ideally not run if there are no tests to execute, though Jest's default behavior often handles this.

Examples

Let's imagine a hypothetical scenario where your tests might create a temporary directory.

Example 1: Basic Teardown

Imagine a jest.teardown.ts file.

// jest.teardown.ts
import fs from 'fs';
import path from 'path';

const globalTeardown = async (): Promise<void> => {
  const tempDir = path.join(__dirname, 'temp_test_files');
  if (fs.existsSync(tempDir)) {
    console.log('Cleaning up temporary test directory...');
    fs.rmSync(tempDir, { recursive: true, force: true });
    console.log('Temporary directory removed.');
  }
};

export default globalTeardown;

Jest Configuration (jest.config.ts):

// jest.config.ts
import type { JestConfigWithTsJest } from 'ts-jest';

const config: JestConfigWithTsJest = {
  preset: 'ts-jest',
  testEnvironment: 'node',
  globalTeardown: '<rootDir>/jest.teardown.ts', // Path to your teardown file
  // ... other Jest configurations
};

export default config;

Explanation:

When Jest runs, after all tests are done, it will look for the file specified in globalTeardown. It will then execute the default exported function (globalTeardown) from that file. In this example, the function checks for a temp_test_files directory and removes it if it exists. The console.log statements would appear in the Jest output after all test results.

Constraints

• The globalTeardown function must be an async function or return a Promise.
• Jest version must be ^27.0.0 or later.
• Your project must be configured to use TypeScript with Jest (e.g., via ts-jest).

Notes

• The globalTeardown function runs after afterAll hooks for individual test files.
• The globalTeardown file is executed from the root of your project directory. Use <rootDir> in your jest.config.ts to correctly reference files relative to the project root.
• Consider how to handle potential errors within your teardown function to ensure it doesn't disrupt the overall Jest reporting.
• Think about what resources might be shared across your entire test suite that would benefit from a single cleanup operation.