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Testing Pyramid

Practical reference for test levels, tooling, and strategy. Based on: The Testing Pyramid: Everybody Knows It, Nobody Follows It

The Pyramid

        ▲
       /E2E\        few — critical user flows only
      /─────\
     /       \
    / Integra-\     moderate — component interactions, API contracts
   /  tion     \
  /─────────────\
 /               \
/   Unit Tests    \  many — all business logic, validation, edge cases
/─────────────────\
Layer Speed Count Tool
Unit 0.001–0.01 s Thousands pytest
Integration 0.1–1 s Hundreds pytest + Playwright APIRequestContext
E2E 5–30 s Tens Playwright (browser)

Sections

1. Unit Tests

File Topics
Concept & Examples Isolation, fast feedback, pytest marks, coverage, typing
Common Mistakes Missing assertions, hidden dependencies, no isolation

2. Integration Tests

File Topics
Concept & Examples Real HTTP via Playwright APIRequestContext, fixtures, cleanup
Common Mistakes Shared state, test-order dependence, over-mocking

3. E2E Tests

File Topics
Concept & Examples Browser automation with Playwright, stable locators, user flows
Common Mistakes Fragile selectors, no auto-wait, testing every validation E2E

4. Pyramid Strategy

File Topics
Shape, Anti-Patterns & Alternatives Ice cream cone, Testing Trophy, microservice contracts, CI timing

Quick Decision Guide

What you need to test Level
Single function, validation rule, calculation Unit
API endpoint → database round trip Integration
Service A calls Service B Integration
User completes a full workflow in browser E2E
Field-level form validation in the UI Unit (not E2E)
Auth contract between two services Integration (contract)

Anti-Pattern: Ice Cream Cone

/─────────────────\
/   E2E (many!)    \  ← slow, flaky, 40+ min CI
/─────────────────\
     /       \
    / Integra-\     ← almost none
   /  tion     \
  /─────────────\
       /  \
      /Unit\         ← barely any
     /──────\

Happens when teams skip unit and integration tests during development and try to cover everything with Playwright at the end.

See also