For it('should find user'), I'm going to get started by making a variable called userId and I'm going to set this equal to the ID I want to use. I need a valid ID so I'm going to go ahead and use 2. 1, 2, or 3 would have worked here:

it('should find user', () => {
  var userId = '2';
});

Next up I am going to go ahead and make a user variable, this is going to be the return result from getUser. I'll set it equal to users.getUser, and we're going to try to fetch a user whose ID is 2 by passing in userId:

it('should find user', () => {
  var userId = '2';
  var user = users.getUser(userId);
});

Now the next thing we're going to do is make an assertion about what we get back, we should have gotten our object back and we can expect that user.id equals, using toBe, and the ID, the userId variable:

it ('should find user', () => {
   var userId = '2';
   var user = users.getUser(userId);
   expect(user.id).toBe(userId);
});

I'm going to go ahead and save the test suite, and you can see all our test cases are still passing, which is fantastic. If it does not equal the ID, maybe the ID is 3, you're going to see the test case fail, and we do get a pretty clear error message:

We get Expected 2 to be 3, which clearly is not the case. This is the final test case though and we can move on to it('should not find user').