sdlc-test

name

sdlc-test

description

Use BEFORE generating implementation code for any feature with verifiable behavior. Writes the tests (and evals, if output quality is judgment-based) FIRST, as the contract that defines "correct," so the agent implements against a real target instead of a vibe check. Make sure to use this whenever you say "implement", "write the code for", "build the function/endpoint/feature" - intercept and do tests first - and also on "write tests" or "add coverage". Third step of the SDLC loop and the single highest-leverage habit.

sdlc-test - write the contract before the code

Third beat of the SDLC loop, and the paper's #1 individual practice: write tests and evals before generating code. A well-written test/eval suite communicates intent more precisely than any prompt and is what turns vibe coding into agentic engineering. It also gives the agent a target to self-correct against.

Why this matters

Tests and evals are how you tell the agent what "correct" means in a form it can check itself - the feedback loop that lets it iterate to green instead of you eyeballing output. Tests catch the deterministic failures; evals catch the non-deterministic ones. Without both, it's vibe coding no matter how good the prompt was.

Tests vs. evals (use the right one)

• Tests - deterministic behavior: given input X, produce output Y. Compiles, returns 3, handles the empty list. Most features need these.
• Evals - non-deterministic / judgment behavior: did an agent or LLM-backed feature produce a response that meets a quality bar? Scored by a rubric, not an assertion. Only needed when the output is a judgment, not a fact.

Procedure

1. Turn success criteria into tests. Take the criteria and edge cases from sdlc-plan and write a test for each - especially the unhappy paths. Edge cases without a test tend to never get handled.
2. Make them fail first. Run the tests against no/empty implementation and confirm they go red. A test that passes before any code is a test that proves nothing.
3. Add an eval rubric only if output is judgment-based. Score the few things a test can't: does it meet intent, is the approach sane. Keep it small (see sdlc-review's rubric).
4. Keep tests behavioral. Test through public interfaces, not implementation details (per AGENTS.md), so they survive refactors.

Output

• Test files covering criteria + edge cases, confirmed red.
• (Only if needed) a short eval rubric file.

Gate

Tests exist and fail before sdlc-implement writes code. The definition of "done" for implementation is: these go green.

References

Load these as needed:

• references/test-and-eval-patterns.md - test types, behavioral testing, and when to use evals.
• references/tdd-with-agents-sop.md - the step-by-step tests-before-code SOP and when to relax it.