There are several ways that you could create tests for your application; one of the possible options is to create unit tests for your application.
If we decided to create unit tests for our client application, we would need a way to mock the connection with our servers; this would involve creating a new (and slightly complex) build for our tests.
We could also create end to end tests, to test the whole flow of a user. Doing this would probably involve using some external tool to run our tests in the context of a browser and automatize the user input. This would also involve an extra step of running a tool such as Selenium or CasperJS.
There are several books on the different ways you can test a frontend application. Here I'm choosing to implement the simplest solution, which involves creating a page for the test using mocha as explained in Chapter 7, Something is Wrong - Testing and...
