What are some practical examples of Sinon.js in action?

What are some practical examples of Sinon.js in action?

Sinon.js is a powerful library for creating spies, mocks, and stubs in JavaScript. For example, you can use it to test AJAX calls by stubbing the XMLHttpRequest.

Can you show me a code snippet for stubbing an AJAX call?

Sure! Here's a simple example:

const xhr = sinon.useFakeXMLHttpRequest();
const requests = [];

xhr.onCreate = function (xhr) {
  requests.push(xhr);
};

// Your AJAX call here

// Later in your test, you can assert on the requests:
requests[0].respond(200, { 'Content-Type': 'application/json' }, JSON.stringify({ success: true }));

What about using spies? How do they work?

Spies allow you to track function calls. For example:

const myFunction = sinon.spy();
myFunction();
console.log(myFunction.called); // true