Design a test strategy on the pyramid: map defect classes to the cheapest test level that catches them, prioritize by risk, use coverage as a floor and mutation testing as the quality truth, and decide what not to test.
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---
name: test-strategy-design
description: "Design a test strategy on the pyramid: map defect classes to the cheapest test level that catches them, prioritize by risk, use coverage as a floor and mutation testing as the quality truth, and decide what not to test."
---
# Test Strategy Design
**Purpose:** a suite that catches real defects cheaply.
## The pyramid
```
/\ few E2E (critical journeys)
/--\ some integration (component interactions)
/----\ many unit (logic) — fast & deterministic
```
Invert the **ice-cream cone** (mostly E2E) — it's slow and flaky.
## Match level to defect
- Logic bug -> **unit**
- Component/contract interaction -> **integration**
- Critical user journey -> **E2E** (few)
## Coverage vs quality
Line/branch coverage = **floor** (finds untested code). **Mutation testing** = truth (does the suite fail when code is wrong?). Decide what NOT to test (trivial getters, framework, third-party).
