Testing Principles (Cross-Cutting)

Shared testing principles for all modules (backend, frontend, common, render-wasm, plugins). Module-specific commands and helpers are in each module's own testing memory.

Core Principles

Test State, Not Interactions — assert on outcomes, not method calls; survives refactoring
DAMP over DRY — tests are specifications; duplication OK if each test is self-contained and readable
Prefer Real Implementations — hierarchy: Real > Fake > Stub > Mock; mock only at boundaries (network, filesystem, email)
Arrange-Act-Assert — every test: setup / action / verify
One Assertion Per Concept — each test verifies one behavior; split compound assertions
Descriptive Test Names — names read like specifications

Anti-Patterns

Testing implementation details → breaks on refactor
Flaky tests (timing, order-dependent) → erode trust
Mocking everything → tests pass, production breaks
No test isolation → pass individually, fail together
Testing framework code → waste of time
Snapshot abuse → nobody reviews, break on any change

Verification Checklist

After completing any implementation:

Every new behavior has a corresponding test
All tests pass for touched modules
Bug fixes include a reproduction test that failed before the fix
Test names describe the behavior being verified
No tests were skipped or disabled

Red Flags

Writing code without corresponding tests
Tests that pass on the first run (may not be testing what you think)
Bug fixes without reproduction tests
Tests that test framework behavior instead of app behavior
Skipping tests to make the suite pass

Rationalizations

"I'll write tests after" → you won't; they'll test implementation not behavior
"Too simple to test" → simple gets complicated; test documents expected behavior
"Tests slow me down" → they speed up every future change
"I tested manually" → manual testing doesn't persist
"Code is self-explanatory" → tests ARE the specification
"Just a prototype" → prototypes become production; test debt accumulates

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