FAIL checkout.test.js ✕ calculateTax should add 8% sales tax (5ms) ✕ applyDiscount should not apply to non-VIP (2ms) The tests screamed instantly. The broken line was caught before it ever reached production.
"So," she said. "Did Mosh save you?"
"That’s it," Sarah said, her voice eerily calm. "You’re not writing a single line of new code until you learn how to test the old code." -Code With Mosh- Mastering JavaScript Unit Testing
He wrote his first failing test: