Test-driven development (TDD) is like playing a game where you have to build something with Lego blocks. Before you start building, you first decide what you want to build and how you’ll know when it’s finished. Then, you take out a small pile of blocks and make a simple test structure to make sure your plan works.
If your test structure falls apart or doesn’t look right, you make changes until it does. Once you’re happy with your test structure, you start building the real thing using the same blocks. Every time you add a new piece to your creation, you make sure it still passes the test. If it doesn’t, you make changes until it does.
In TDD, instead of Lego blocks, you’re writing code for a computer program. The tests you create are like the test structure you made with the Lego blocks – they tell you if your code works the way it should. By testing your code every step of the way, you can be confident that it will work correctly when you’re finished.