> For the complete documentation index, see [llms.txt](https://docs.thecolliery.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.thecolliery.org/tools/canaries/skill-8.md).

# testability-canary

Testability and design decoupling canary — checks for tight coupling, lack of Dependency Injection (DI), hardcoded constructors, Single Responsibility Principle (SRP) violations, and mockability gaps.

Audit code to ensure it is decoupled, modular, and easy to cover with automated tests.

## Auditing Categories

1. **Hardcoded Constructors** — instantiating deps inside classes (`new DatabaseClient()`) instead of injecting via constructor/factory (prevents mocking).
2. **SRP Violations** — a class or method doing too many distinct duties (e.g. a service that also parses JSON and formats UI).
3. **Static Dependencies** — reliance on global static methods or Singletons that make test isolation impossible.
4. **Time & Environment Coupling** — direct `DateTime.Now`, `fs`, or `process.env` calls without an abstraction layer (fragile time/path-sensitive tests).
5. **Private Logic Gaps** — complex business logic hidden in private methods that can't be tested directly (extract to testable helpers).

Per-stack patterns and the mock-strategy vocabulary: read `references/checks.md` before scanning.

## Fix mode (choice-gated)

In Agent Context, after the report, present via `ask_question`:

* **Apply safe refactoring:** extract hardcoded initializations into constructor params (DI) + add interface definitions. Each fix: checkpoint (copy the touched file(s) aside, or use an isolated worktree — never `git stash`/`git commit`, which can hide or include unrelated staged/unstaged user work) → record a build+test BASELINE → apply → build + tests → auto-revert only if a NEW failure appeared versus the baseline.
* **Let me pick:** user selects specific refactoring moves.
* **Report only:** exit unchanged.

## Grants & denials (CLASSIFY-BLOCK)

| class | step it powers                                                                                                | grant                                             | on denial                                                                                  |
| ----- | ------------------------------------------------------------------------------------------------------------- | ------------------------------------------------- | ------------------------------------------------------------------------------------------ |
| read  | scan coupling/DI surfaces for the categories above                                                            | `Read`·`Grep`·`Glob`                              | refuse that file, name it — never a clean bill                                             |
| write | Fix mode's safe-refactor apply, incl. checkpoint → baseline → build+tests → auto-revert only on a NEW failure | `Edit`·`Bash` (checkpoint/build/revert need exec) | report the fix as NOT applied AND the checkpoint/revert as NOT available, never claim done |

## Output

`| file:line | coupling point | severity | finding | mock strategy |`

Severity: CRITICAL (un-mockable external write/network call) · HIGH (SRP violation blocking unit testing) · MEDIUM (time/env coupling) · LOW (minor static dependency)


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# Agent Instructions
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## Querying This Documentation
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```
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```

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