test-driven-development

The test-driven development (TDD) cycle is a practice where you write a failing test before any implementation code, guaranteeing the test verifies behavior. This Red-Green-Refactor process prevents bugs by ensuring code is written only to pass predefined tests.

To write tests first for a new feature, begin by creating a test that defines the expected behavior and observe it fail. Then, write the minimal amount of implementation code necessary to make that failing test pass, ensuring correct functionality from the outset.

Yes, you can use test-driven development for bug fixes and refactoring existing code. The methodology applies to all software development tasks by guiding you to write a failing test that reproduces the bug before writing the fix or updating the code.

The best way to ensure tests verify behavior is to write the test first and observe it fail. This rigorous development practice guarantees the test is actually checking the expected behavior, preventing regressions when you write the minimal code to pass it.

A strict test-first approach might be less suitable for agile development tasks involving exploratory prototyping or undefined behavior, as the methodology requires writing a failing test that defines expected behavior before any implementation code can be written.