Over inside of server.test.js we can get started down at the very bottom by adding a describe block. I'm going to call describe, and this describe block will be named GET /todos/:id, and we can add our arrow function (=>) as the callback function. Inside of our describe callback we can now set up the test case that we're going to create together, it('should return todo doc'). This is going to be the test that makes sure that when we pass in a valid ID that does match a doc, the doc comes back. It's going to be an asynchronous test, so we will be specifying the done argument:
describe('GET /todos/:id', () => { it('should return todo doc', (done) => { }); });
Now, in order to run this test case we're going ...