| name | testability-canary |
| description | Testability and design decoupling canary — checks for tight coupling, lack of Dependency Injection (DI), hardcoded constructors, Single Responsibility Principle (SRP) violations, and mockability gaps. Triggers on keywords: "/testability-canary", "testability-canary", "testability audit", "decoupling". Use when refactoring coupling, introducing DI, or making code unit-testable. |
Testability Canary (Decoupling & Mockability Audit)
Audit code to ensure it is decoupled, modular, and easy to cover with automated tests.
Auditing Categories
- Hardcoded Constructors — instantiating deps inside classes (
new DatabaseClient()) instead of injecting via constructor/factory (prevents mocking).
- SRP Violations — a class or method doing too many distinct duties (e.g. a service that also parses JSON and formats UI).
- Static Dependencies — reliance on global static methods or Singletons that make test isolation impossible.
- Time & Environment Coupling — direct
DateTime.Now, fs, or process.env calls without an abstraction layer (fragile time/path-sensitive tests).
- 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 (git stash/commit in a git repo; else copy the file aside — never assume git) → apply → build + tests → auto-revert if newly red.
- Let me pick: user selects specific refactoring moves.
- Report only: exit unchanged.
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)
