What are Chai async assertions and how do I use them?

What are Chai async assertions and how do I use them?

Chai async assertions are used in testing to handle asynchronous code. They allow you to write tests that wait for promises to resolve.

Can you give me an example of how to use them in a test?

Sure! You can use chai-as-promised to assert that a promise resolves to a specific value. For example:

const { expect } = require('chai');
const chaiAsPromised = require('chai-as-promised');
chai.use(chaiAsPromised);

it('should resolve to 42', function() {
  return expect(Promise.resolve(42)).to.eventually.equal(42);
});

What if the promise is rejected?

If the promise is rejected, you can use to.be.rejected to assert that it fails. For example:

it('should be rejected with an error', function() {
  return expect(Promise.reject(new Error('fail'))).to.be.rejectedWith('fail');
});

Are there any other libraries I should consider for async testing?

Yes, you might also consider using libraries like Mocha for structuring your tests or Jest, which has built-in support for async testing.