Starting... This lab is to help our codes to make sure working well. Instead of manual testing for our functions, there are a lot of automatic test framwork for any languages. Since I used node js for my application, I chose jest since it looked very convenient and easy for me . Progressing... Jest, link , is great test frame work since it provides more than mocha and I heard it is maintained by facebook... but not sure. To use this, I installed it as a development package and simply put some scripts such as test and test:coverage. To be honest, for me it was not really easy as what I have heard. I need to understand the mocking function or fake implementation which made me so confused when I met it at first such as jest.fn() and mockImplementation(). To be honest, I am not a fan of test cases yet, I really have no idea for some parts how to test maybe I need more time to be familiar with it. Moreover, I think I should have not implemented the current way like a lot o...