What are the differences between popular assertion libraries?

What are the differences between popular assertion libraries like Chai, Jest, and Mocha?

Chai is known for its expressive syntax and flexibility, allowing for behavior-driven development. Jest is a complete testing framework with built-in assertion capabilities, making it easy to set up and use. Mocha is a test framework that can be paired with various assertion libraries, offering more customization.

Which one should I use for a new project?

It depends on your project's needs. If you want an all-in-one solution, Jest is great. For more flexibility, Chai with Mocha might be better.

Can you give examples of how to use each library?

Sure! For Chai, you might use expect(value).to.equal(expectedValue). In Jest, you would use expect(value).toBe(expectedValue). For Mocha with Chai, it would be similar to Chai's syntax.

Are there any performance differences between them?

Generally, Jest is optimized for performance with features like parallel test execution. Chai and Mocha may be slower due to their flexibility and additional setup.