Go Testing

---
name: go-testing
description: 'Trigger: Go tests, go test coverage, Bubbletea teatest, golden files.
  Apply focused Go testing patterns.'
license: Apache-2.0
metadata:
  author: gentleman-programming
  version: '1.0'
---

## Activation Contract

Load this skill when writing or reviewing Go tests, adding coverage, testing Bubbletea/TUI flows, using `teatest`, or updating golden files.

## Hard Rules

- Prefer table-driven tests for multiple cases; use `t.Run(tt.name, ...)`.
- Test behavior and state transitions, not implementation trivia.
- Use `t.TempDir()` for filesystem tests; never rely on a real home directory.
- Keep integration tests skippable with `testing.Short()` when they run external commands or slow flows.
- For Bubbletea, test `Model.Update()` directly for state changes; use `teatest` only for interactive flows.
- Golden files must be deterministic; update only through the repo's `-update` path and rerun tests without `-update`.
- Use small mocks/interfaces around system or command execution boundaries.

## Decision Gates

| Target | Test pattern |
|---|---|
| Pure function or parser | Table-driven unit test. |
| Error behavior | Explicit success and failure cases. |
| File operations | `t.TempDir()` plus focused assertions. |
| TUI state transition | Direct `Model.Update()` call with `tea.Msg`. |
| Full TUI interaction | `teatest.NewTestModel()`. |
| Rendered output | Golden file test. |
| Real external command | Integration test; skip in `-short`. |

## Execution Steps

1. Identify behavior under test and the smallest public boundary that proves it.
2. Choose the test pattern from the decision gate.
3. Name cases by scenario, not input mechanics.
4. Assert outputs, errors, state, and side effects explicitly.
5. Run the narrow package test first, then the relevant broader suite.
6. For golden updates: run with `-update`, inspect diff, then rerun without `-update`.

## Output Contract

Report test files changed, scenarios covered, commands executed, golden files updated, and any skipped integration scope.

## References

- [references/examples.md](references/examples.md) — compact table-driven, Bubbletea, teatest, golden, and command examples.