Test-Driven Development is still the best way to build sustainable software
Timeless practices need to be reintroduced to every generation of developers.
TDD was born out of Kent Beck's insight:
"If I test the code I write, I get better quality code. What would happen if I took the process to the extreme: writing tests before the code itself?"
In practice it turned out that writing tests before implementation leads to a more important outcome than having an automated test suite:
aka Good Design.
TDD is a license to write crap code first
This is what "write the simplest thing that could possibly work to make the tests pass" is about.
Because at first you're doing something else: decomposing a problem and exploring a design solution.
Once the you've discovered a solution, having an umbrella of tests gives you peace of mind and immediate feedback as you polish the code one small step—and passed test—at a time.
Without fast feedback, developers simply can't do their job well.
Finally, TDD enables every team to work the same way on day 1 and day 1,000: in continuous cycles of very short iterations, without worry.
👉 For a more systematic introduction to Test-Driven Development, read Ferdinando Santacroce's article on Semaphore blog: Test-Driven Development (TDD): A Time-Tested Recipe for Quality Software.