Note that the previous logic will indiscriminately return a 400 response, even if the payload is not empty. This is fine because the TDD process encourages you to write the minimum amount of code possible to make the tests pass, and so far we have only written a test for the empty payload scenario.
The rationale behind this is to ensure you are not falling into the trap of coding something that you don't need. This principle has been summarized in the phrase "You ain't gonna need it," or YAGNI, which is a principle that originated from extreme programming (XP). The original states that you should "always implement things when you actually need them, never when you just foresee that you need them". You may have ...
