Now that we have Mocha installed, we can go ahead and create a test file. In the utils folder, we'll make a new file called utils.test.js:
This file will store our test cases. We'll not store our test cases in utils.js. This will be our application code. Instead, we'll make a file called utils.test.js. When we use this test.js extension, we're basically telling our app that this will store our test cases. When Mocha goes through our app looking for tests to run, it should run any file with this extension.
Now we have a test file, the only thing left to do is create a test case. A test case is a function ...
