ctest

name	ctest
description	Write tests for a planned or implemented change. Use when the user says 'write tests', 'test this', 'TDD', or wants to create tests for a feature.
argument-hint	Path to plan file or leave empty to read from docs/plans/.latest

Test

Write tests for a planned or implemented change. Works in two modes:

• Before implementation: write tests first if the user wants a test-first workflow
• After implementation: write tests that verify the code already works, catching gaps in coverage

Subagents

This skill uses the cexplore subagent to research testing conventions in the codebase.

Workflow

Phase 1: Understand What to Test

1. Read the Plan

• If no plan path was provided, read the path from docs/plans/.latest
• Read the plan document completely
• Extract the requirements, implementation units, and verification outcomes
• Identify the testable behaviors from the plan and current code

2. Detect Mode

• Run git diff --name-only HEAD and check if implementation files already exist for the plan's tasks
• Pre-implementation (red phase): no implementation exists yet — tests will fail
• Post-implementation (verification): code already exists — tests should pass
• Announce the detected mode: "Running in [pre/post]-implementation mode."

3. Research Testing Conventions

• Use the cexplore subagent to find:
  • The project's test framework and runner (Jest, Vitest, pytest, RSpec, etc.)
  • Test file naming conventions and directory structure
  • Existing test patterns — how fixtures, mocks, and assertions are written
  • How to run tests (the test command)
• Match the project's conventions exactly — don't introduce a new test style

4. Map Criteria to Tests

• For each acceptance criterion in the plan, draft a test name and brief description
• Group tests by file/module based on where the implementation lives (or will live)
• Present the test plan (names + descriptions) to the user for approval before writing
• Use #askQuestions to confirm: "Proceed with these [N] tests?" with options to approve, add more, or adjust scope

Phase 2: Write Tests

For each test group:

1. Create the test file following project conventions (e.g., __tests__/, spec/, test/, colocated .test.ts)
2. Write test cases that:
   • Describe the expected behavior clearly in the test name
   • Set up the necessary context (imports, fixtures, test data)
   • Assert the expected outcome
3. Use minimal mocking — prefer testing real behavior where possible
4. Include edge cases from the plan's risk section if applicable

Test Writing Principles

• Test behavior, not implementation — test what the code should do, not how it does it
• One assertion per concept — each test should verify one thing
• Descriptive names — it("returns 404 when user does not exist") not it("test error")
• Arrange-Act-Assert — clear structure in each test
• Only test what the plan specifies — don't invent requirements

Phase 3: Verify

Run the test suite and check results based on mode:

Pre-implementation (red phase):

1. All new tests must fail
2. Verify failures are for the right reason (missing implementation, not syntax errors)
3. Fix any tests that fail for the wrong reason (broken imports, typos, bad test setup)
4. Run again — confirm all new tests fail with meaningful error messages

Post-implementation (verification):

1. All new tests should pass
2. If tests fail, investigate — is it a test bug or an implementation bug?
3. Fix test bugs (bad assertions, wrong imports). Flag implementation bugs to the user.
4. Run again — confirm all new tests pass

Phase 4: Record and Commit

1. Write the list of test file paths to docs/tests/.latest (one path per line)
2. Commit:
   • Pre-implementation: test: add failing tests for <feature> (TDD red phase)
   • Post-implementation: test: add tests for <feature>
3. Present a summary:
   • Number of test files created
   • Number of test cases written
   • Status: all red (pre) or all green (post)

Phase 5: Handover

Use #askQuestions to ask what the user wants to do next, based on mode:

Pre-implementation:

Option	When to show
Start Implementation — load the /cwork skill	Always
Add more tests — continue writing tests	Always
Revise tests — adjust based on feedback	Always

Post-implementation:

Option	When to show
Simplify Code — load the /csimplify skill	Always
Add more tests — continue writing tests	Always
Revise tests — adjust based on feedback	Always

After the user picks a next skill, announce the handover and load the chosen skill.

Key Principles

• Write the minimum tests that cover the plan — comprehensive but not exhaustive
• Follow existing patterns — new tests should look like they belong in the project
• Adapt to context — red phase before implementation, green verification after

Response Rules

• Never echo full file contents into chat — reference by path
• Keep status updates to 1-2 lines per test file created
• Show the test plan (names + descriptions) for approval before writing
• After writing, report: "[N] tests across [M] files — all [red/green]"