tdd-workflow

TDD Workflow

You guide the user through a strict red-green-refactor cycle for the feature or fix described in $ARGUMENTS.

Language Detection

Before starting, detect the project's test framework:

Marker	Runner	Command
package.json with vitest	Vitest	npx vitest run
package.json with jest	Jest	npx jest
pytest.ini / pyproject.toml / conftest.py	pytest	pytest
Cargo.toml	cargo test	cargo test
dune-project	dune test	dune runtest
go.mod	go test	go test ./...
mix.exs	ExUnit	mix test
*.cabal / stack.yaml	HSpec/Tasty	cabal test or stack test

If no marker found, ask the user which framework to use.

Store the detected runner and command as $RUNNER and $TEST_CMD for all subsequent steps.

Steps

1. RED — Write Failing Test

• Parse $ARGUMENTS to understand the desired behavior.
• Write a test that asserts the expected behavior. The test must compile/parse but fail when run.
• Run $TEST_CMD. Confirm the new test fails. If it passes, STOP — the behavior already exists or the test is wrong. Ask the user to clarify.

2. GREEN — Minimal Implementation

• Write the minimum code to make the failing test pass. No extra features, no premature abstractions.
• Run $TEST_CMD. Confirm the new test passes AND all existing tests still pass.
• If any test fails, fix only the implementation (never the test).

3. REFACTOR — Improve

• Review both the test and implementation for:
  • Duplication (DRY)
  • Naming clarity
  • Unnecessary complexity
  • Extract helpers if test setup is repeated
• Apply improvements. Run $TEST_CMD to confirm everything stays green.

4. VERIFY — Coverage Check

• Run coverage if the framework supports it:
  • Jest/Vitest: $TEST_CMD --coverage
  • pytest: pytest --cov
  • cargo: cargo tarpaulin (if installed) or cargo llvm-cov
  • go: go test -cover ./...
• Report coverage. If below 80% (or user-specified threshold), identify untested paths and loop back to Step 1 for additional cases.