Test-Driven Development (TDD)

Biological Parallel

Arctic ground squirrels pre-adapt to winter by building fat reserves months before freezing begins—survival depends on preparation before crisis arrives. TDD inverts the typical sequence: write the test (define survival criteria) before writing the code (develop the adaptation). Organisms that wait until winter to start preparing die; codebases that wait until production to define correctness criteria accumulate fatal vulnerabilities. The test is the specification for what environmental conditions the code must survive.