For a long time I treated tests as something to write after the feature was 'done'. The result? Tests that only covered happy paths, and bugs that appeared exactly where I didn't test. Writing tests early changed everything.
When you write a test before the implementation, you're forced to think about the contract first: what goes in, what comes out, and what happens on failure. That single shift catches design problems while they're still cheap to fix.
In my internship at BPJS Ketenagakerjaan, embedding testing early meant the AI chatbot features I built could be verified quickly against edge cases — empty inputs, unexpected formats, slow responses. It gave the team confidence to ship.
My advice: start with the critical paths, keep tests fast, and treat the test suite as documentation. Future-you (and your teammates) will thank you.