--- name: test-driven-development description: Unified TDD skill with three input modes — from spec, from task, or from description. Enforces test-first development using repository patterns, with proptest guidance and backpressure integration. type: anthropic-skill version: "1.0.0" --- # Test-Driven Development ## Overview One skill for all TDD workflows. Enforces test-first development using existing repository patterns. Three input modes handle different entry points — specs, task files, or ad-hoc descriptions — but the core cycle is always RED → GREEN → REFACTOR. ## Input Modes Detect the input type and follow the corresponding mode: ### Mode A: From Spec (`.spec.md`) Use when the input references a `.spec.md` file with Given/When/Then acceptance criteria. 1. **Locate and parse** the spec file — extract all Given/When/Then triples 2. **Generate one test stub per criterion** with `todo!()` bodies: ```rust /// Spec: — Criterion # /// Given /// When /// Then #[test] fn _criterion__() { todo!("Implement: "); } ``` 3. **Verify stubs compile** but fail: `cargo test --no-run -p ` 4. Proceed to the [TDD Cycle](#tdd-cycle) to make stubs pass **Programmatic support:** `ralph_core::preflight::{extract_acceptance_criteria, extract_criteria_from_file, extract_all_criteria}` can parse criteria from spec files. ### Mode B: From Task (`.code-task.md`) Use when the input references a `.code-task.md` file or a specific implementation task. 1. **Read the task** and identify acceptance criteria or requirements 2. **Discover patterns** (see [Pattern Discovery](#pattern-discovery)) 3. **Design test scenarios** covering normal operation, edge cases, and error conditions 4. **Write failing tests** for all requirements before any implementation 5. Proceed to the [TDD Cycle](#tdd-cycle) ### Mode C: From Description Use for ad-hoc tasks without a spec or task file. 1. **Clarify requirements** from the description 2. **Discover patterns** (see [Pattern Discovery](#pattern-discovery)) 3. **Write failing tests** targeting the described behavior 4. Proceed to the [TDD Cycle](#tdd-cycle) ## Pattern Discovery Before writing tests, discover existing conventions: ```bash rg --files -g "crates/*/tests/*.rs" rg -n "#\[cfg\(test\)\]" crates/ ``` Read 2-3 relevant test files near the target code. Mirror: - Test module layout, naming, and assertion style - Fixture helpers and test utilities - Use of `tempfile`, scenarios, or harnesses ## TDD Cycle ### 1) RED — Failing Tests - Write tests for the exact behavior required - Run tests to confirm failure **for the right reason** - If tests pass without implementation, the test is wrong ### 2) GREEN — Minimal Implementation - Write the minimum code to make tests pass - No extra features or refactoring during this step ### 3) REFACTOR — Clean Up - Improve implementation and tests while keeping tests green - Align with surrounding codebase conventions - Re-run tests after every change ## Proptest Guidance Use `proptest` only when ALL of: - Function is pure (no I/O, no time, no globals) - Deterministic output for given input - Non-trivial input space or edge cases ```rust proptest! { #[test] fn round_trip(input in "[a-z0-9]{0,32}") { let encoded = encode(input.as_str()); let decoded = decode(&encoded).expect("should decode"); prop_assert_eq!(decoded, input); } } ``` Don't introduce proptest as a new dependency without strong justification. ## Backpressure Integration Include coverage evidence in completion events: ```bash ralph emit "build.done" "tests: pass, lint: pass, typecheck: pass, audit: pass, coverage: pass (82%)" ``` Run `cargo tarpaulin --out Html --output-dir coverage --skip-clean` when feasible. If coverage cannot be run, state why and include targeted test evidence instead. ## Test Location Rules - Spec maps to a single module → inline `#[cfg(test)]` tests - Spec spans multiple modules → integration test in `crates//tests/` - CLI behavior → `crates/ralph-cli/tests/` - Follow existing patterns in the target crate ## Anti-Patterns - Writing implementation before tests - Generating tests that pass without implementation - Copying tests from other crates without adapting to local patterns - Adding proptest when a simple example test suffices - Emitting completion events without coverage evidence

test-driven-development

Description

Latest Changes

Install test-driven-development with One Click