The red-green-refactor process is the most important part of TDD. It is the main pillar, without which no other aspect of TDD will work.
The name comes from the states our code is within the cycle. When in red state, code does not work; when in the green state, everything is working as expected, but not necessarily in the best possible way. Refactor is the phase when we know that features are well covered with tests and thus gives us the confidence to change it and make it better.
Every new feature starts with a test. The main objective of this test is to focus on requirements and code design before writing the code. A test is a form of an executable documentation and can be used later on to get an understanding of what the code does or what are the intentions behind it.
At this point, we are in the red state since the execution of tests fails. There is a discrepancy between what tests expect from the code and what the implementation code actually...