Overview
Testing the Handshake
Integration testing is where 'it all comes together.' It uncovers defects in parameter passing, environmental differences, and third-party API inconsistencies.
Many systems fail not because of the logic within a function, but because of the interfaces between services. Integration testing ensures that the contract between Service A and Service B is honored under various data loads.
Best Practices
Dos and Don'ts
Avoid common mistakes that can lead to flaky tests and maintenance nightmares.
What to do
- •Use 'Big Bang' integration only for very small systems; prefer Incremental approaches.
- •Automate your API integration tests using tools like Postman, RestAssured, or Playwright.
- •Focus on data integrity as it passes through various layers (UI to API to DB).
Common Pitfalls
- •Don't wait until all modules are finished; start integrating as soon as two modules can talk.
- •Don't ignore error handling between services (e.g., how does the UI handle a 503 from the API?).
The Details
Top-Down vs. Bottom-Up Strategies
QA Managers must choose an integration strategy based on project architecture. Top-Down starts with high-level modules (UI) and uses stubs for lower levels. Bottom-Up starts with foundational modules (DB/Utilities) and uses drivers to simulate higher levels. A modern 'Sandwich' approach combines both to find critical defects in the middle layer early.