title: What is the `it()` function here doing?
body: <p>The following snippet of code is from <a href="https://docs.angularjs.org/guide/scope" rel="noreferrer">angular's documentation</a>.  What is the <code>it()</code> function here doing (I'm assuming it has some conventional meaning because otherwise no context seems to be given for its meaning)?  I don't see any reference to it on angular's site.  It's also hard to google due to it's name.  The context is with regards to code testing.</p>
  
  <pre><code>it('should say hello', function() {
    var scopeMock = {};
    var cntl = new MyController(scopeMock);
  
    // Assert that username is pre-filled
    expect(scopeMock.username).toEqual('World');
  
    // Assert that we read new username and greet
    scopeMock.username = 'angular';
    scopeMock.sayHello();
    expect(scopeMock.greeting).toEqual('Hello angular!');
  });
  </code></pre>