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itseffiitseffi/agentic-os/.agents/skills/tdd/SKILL.md

tdd

Skill114 starsChanged 10 months agoMITView on GitHub

Test-driven development - write failing test first, then minimal code. Use before implementing any feature or bugfix.

194 other projects use a version of this, 4 of them edited.

Adopted by

Most recently taken up by

Used with

Projects with it also use capture-learning-tools, design-frontend-dev and 10 more.

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Files found in the same public projects as a version of this one, more often than they turn up anywhere else. Each project counts once, large collections count for less, and this file's own repository is left out.
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The file

Show its rules and text

We split this skill into the rules it gives an agent

13 rules. 0 are common, 13 are distinctive, and 0 are very specific to this project.

  • 0

    Common

    Most of the 186 edited versions we read keep these.

  • 13

    Distinctive

    This author's own choices. Worth a look.

  • 0

    Very specific

    Tied to their project's names, files or tools. Probably skip.

  • Common
  • Distinctive
  • Very specific
  1. Distinctive:

    Use when implementing any feature or bugfix, before writing implementation code.

    line 8
  2. Distinctive:

    Write code before the test?

    line 16
  3. Distinctive:

    Don't keep it as "reference"

    line 19
  4. Distinctive:

    Don't "adapt" it while writing tests

    line 20
  5. Distinctive:

    Write one minimal test showing what should happen.

    line 26
  6. Distinctive:

    Run the test, confirm it fails (not errors)

    line 33
  7. Distinctive:

    Test passes? You're testing existing behavior.

    line 35
  8. Distinctive:

    Write simplest code to pass the test.

    line 38
  9. Distinctive:

    Don't add behavior beyond the test

    line 41
  10. Distinctive:

    Keep tests green. Don't add behavior.

    line 54
  11. Distinctive:

    Before marking work complete:

    line 89
  12. Distinctive:

    Use this skill when the task directly matches the workflow described above.

    line 101
  13. Distinctive:

    Do not use this skill when the request is unrelated, low-stakes, or better handled by a simpler direct response.

    line 105

“Common” is measured: kept by at least 6 in 10 of the 186 edited versions of this file we could read. “Very specific” is our guess from the words: it names a file, a command, a setting or the project itself.

Keep what fits and drop the rest. Your version, ready for your agents.
Files
SKILL.md

Test-Driven Development (TDD)

Use when implementing any feature or bugfix, before writing implementation code.

The Iron Law

NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST

Write code before the test? Delete it. Start over.

No exceptions:

  • Don't keep it as "reference"
  • Don't "adapt" it while writing tests
  • Delete means delete

Red-Green-Refactor

RED - Write Failing Test

Write one minimal test showing what should happen.

  • One behavior
  • Clear name
  • Real code (no mocks unless unavoidable)

Verify RED - Watch It Fail

MANDATORY. Never skip.

  • Run the test, confirm it fails (not errors)
  • Failure message is expected
  • Test passes? You're testing existing behavior. Fix test.

GREEN - Minimal Code

Write simplest code to pass the test.

  • Just enough to pass
  • No extra features
  • Don't add behavior beyond the test

Verify GREEN - Watch It Pass

MANDATORY.

  • Test passes
  • Other tests still pass
  • Output pristine (no errors, warnings)

REFACTOR - Clean Up

After green only:

  • Remove duplication
  • Improve names
  • Extract helpers Keep tests green. Don't add behavior.

Why Order Matters

"I'll write tests after" Tests written after pass immediately. Passing immediately proves nothing. Test-first forces you to see the test fail, proving it actually tests something.

"Tests after achieve same goals" No. Tests-after answer "What does this do?" Tests-first answer "What should this do?"

"Deleting X hours of work is wasteful" Sunk cost fallacy. The time is gone. The waste is keeping code you can't trust.

Red Flags - STOP and Start Over

  • Code before test
  • Test after implementation
  • Test passes immediately
  • "I already manually tested it"
  • "Tests after achieve the same purpose"
  • "This is different because..."

All mean: Delete code. Start over with TDD.

Common Rationalizations

ExcuseReality
"Too simple to test"Simple code breaks. Test takes 30 seconds.
"I'll test after"Tests passing immediately prove nothing.
"Already manually tested"Ad-hoc ≠ systematic. No record, can't re-run.
"TDD will slow me down"TDD faster than debugging later.

Verification Checklist

Before marking work complete:

  • Every new function/method has a test
  • Watched each test fail before implementing
  • Each test failed for expected reason
  • Wrote minimal code to pass each test
  • All tests pass
  • Output pristine (no errors, warnings)

Can't check all boxes? You skipped TDD. Start over.

When to Use

Use this skill when the task directly matches the workflow described above.

When Not to Use

Do not use this skill when the request is unrelated, low-stakes, or better handled by a simpler direct response.

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