Exercises.md

Exercises

Some suggested exercises. The purpose is to learn mocking. If you come with your own, pursue them!

The exercises

1. Controller - Service interaction

   The controller returns an empty list. Using TDD, drive forward an implementation that calls the service. Hint: use Mockito.verify.

   The service has no method yet, let the test tell you what it should be like.

2. Service implementation

   Switch to the service. Still no implementation of the method called by the controller, you should have a stub by now. Use TDD to create an implementation where you handle the cases, nothing in the database, something in the database and broken database. Hint: Mockito.when with thenReturn and with thenThrow.

   There is some test code already. Use it for inspiration.

    Sidenote: Exception handling in a micro service is a bit different. You generally have
    an exception mapper that returns standard Http status codes, such as 404
    for something not found. Therefore, checked exceptions are not used.
    
    See the class ExceptionHandling for more on this. 
   

3. Capture the call

   Create a Post method in the controller that creates a new album. Hint: use @PostMapping annotation and define a class for the body, perhaps CreateAlbumRequest?

   The controller should get help from a service method in the same pattern as above.

   The AlbumEntity should have a UUID as primary key and we will let the application, not the database, generate it (UUID.randomUUID().toString()). Verify that the service calls save on the repository with a new UUID.

   Hint: use ArgumentCaptor, see the README.

Live

Of course you like to try it out with the browser.

If you have a database running as instructed in the ReadMe, it should be possible to get the application started. The main class is ThebandApplication. Test http://localhost:5705/albums to see it return an empty list.