Test-Driven Development

The Essence

TDD is a design workflow, not a testing technique. Writing a test is an interface design act — you decide how a behavior should be called. Making it pass is a learning act — you discover the simplest implementation. Refactoring is an implementation design act — you improve internal structure.

Every behavior is born from this cycle:

Describe the behavior in a test → Make it real → Clean up

A test that errors on import is not a failing test. A cycle that stops at RED is not a cycle.

Workflow Overview