lmiranda
2d51df7a42
Phase 1b: Rename all ~94 commands across 12 plugins to /<noun> <action> sub-command pattern. Git-flow consolidated from 8→5 commands (commit variants absorbed into --push/--merge/--sync flags). Dispatch files, name: frontmatter, and cross-reference updates for all plugins. Phase 2: Design documents for 8 new plugins in docs/designs/. Phase 3: Scaffold 8 new plugins — saas-api-platform, saas-db-migrate, saas-react-platform, saas-test-pilot, data-seed, ops-release-manager, ops-deploy-pipeline, debug-mcp. Each with plugin.json, commands, agents, skills, README, and claude-md-integration. Marketplace grows from 12→20. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
84 lines
2.6 KiB
Markdown
84 lines
2.6 KiB
Markdown
---
|
|
description: Mocking, stubbing, and dependency injection strategies for tests
|
|
---
|
|
|
|
# Mock Patterns Skill
|
|
|
|
## Overview
|
|
|
|
Mocking strategies and best practices for isolating code under test from external dependencies.
|
|
|
|
## When to Mock
|
|
|
|
| Situation | Mock? | Reason |
|
|
|-----------|-------|--------|
|
|
| External API calls | Yes | Unreliable, slow, costs money |
|
|
| Database queries | Depends | Mock for unit, real for integration |
|
|
| File system | Depends | Mock for unit, tmpdir for integration |
|
|
| Time/date functions | Yes | Deterministic tests |
|
|
| Random/UUID generation | Yes | Reproducible tests |
|
|
| Pure utility functions | No | Fast, deterministic, no side effects |
|
|
| Internal business logic | No | Test the real thing |
|
|
|
|
## Python Mocking
|
|
|
|
### unittest.mock / pytest-mock
|
|
|
|
```
|
|
patch("module.path.to.dependency") # Replaces at import location
|
|
patch.object(MyClass, "method") # Replaces on specific class
|
|
MagicMock(return_value=expected) # Creates callable mock
|
|
MagicMock(side_effect=Exception("e")) # Raises on call
|
|
```
|
|
|
|
**Critical rule:** Patch where the dependency is USED, not where it is DEFINED.
|
|
- If `views.py` imports `from services import send_email`, patch `views.send_email`, NOT `services.send_email`.
|
|
|
|
### pytest-mock (preferred)
|
|
|
|
Use the `mocker` fixture for cleaner syntax:
|
|
- `mocker.patch("module.function")` — auto-cleanup after test
|
|
- `mocker.spy(obj, "method")` — record calls without replacing
|
|
|
|
## JavaScript Mocking
|
|
|
|
### Jest
|
|
|
|
```
|
|
jest.mock("./module") // Auto-mock entire module
|
|
jest.spyOn(object, "method") // Spy without replacing
|
|
jest.fn().mockReturnValue(value) // Create mock function
|
|
```
|
|
|
|
### Vitest
|
|
|
|
```
|
|
vi.mock("./module") // Same API as Jest
|
|
vi.spyOn(object, "method")
|
|
vi.fn().mockReturnValue(value)
|
|
```
|
|
|
|
## Mock vs Stub vs Spy
|
|
|
|
| Type | Behavior | Use When |
|
|
|------|----------|----------|
|
|
| **Mock** | Replace entirely, return fake data | Isolating from external service |
|
|
| **Stub** | Provide canned responses | Controlling specific return values |
|
|
| **Spy** | Record calls, keep real behavior | Verifying interactions without changing behavior |
|
|
|
|
## Dependency Injection Patterns
|
|
|
|
Prefer DI over mocking when possible:
|
|
- Constructor injection: pass dependencies as constructor args
|
|
- Function parameters: accept collaborators as arguments with defaults
|
|
- Context managers: swap implementations via context
|
|
|
|
DI makes tests simpler and avoids brittle mock paths.
|
|
|
|
## Anti-Patterns
|
|
|
|
- Mocking too deep (mock chains: `mock.return_value.method.return_value`)
|
|
- Asserting on mock call counts instead of outcomes
|
|
- Mocking the system under test
|
|
- Not resetting mocks between tests (use autouse fixtures or afterEach)
|