API Integration Testing

Build robust test suites for your APIs with integration, contract, and E2E tests.

Testing Pyramid for APIs

Level What It Tests Speed Isolation

Unit Handlers, validators, utils Fast High

Integration API + database, services Medium Medium

Contract API shape vs OpenAPI spec Fast High

E2E Full stack, real DB Slow Low

Key Principles

• Test API behavior through HTTP requests, not internal function calls

• Use real database for integration tests (SQLite or test containers)

• Validate response shapes against OpenAPI spec with contract tests

• Isolate external services with MSW or similar mock servers

Quick Start Checklist

• Set up test framework (Vitest + Supertest recommended)

• Configure test database (separate from dev)

• Create test factories for data setup

• Write integration tests for each endpoint (happy + error paths)

• Add contract tests against OpenAPI spec

• Configure CI pipeline for automated test runs

References

Reference Description

test-frameworks.md Vitest, Jest, Supertest setup and configuration

test-patterns.md Request testing, authentication, error validation

test-data.md Factories, fixtures, database seeding

contract-testing.md OpenAPI validation, schema testing

ci-cd.md CI pipeline configuration, environment setup