What is API Testing?
API testing is a type of software testing that focuses on verifying whether application programming interfaces (APIs) meet expectations in terms of functionality, reliability, performance, and security.
Why API Testing?
- APIs are core to backend services and logic.
- Faster and more stable than UI tests.
- Can detect issues early in the development lifecycle.
- Ensures integration between different services is smooth.
Common Tools for API Testing
- Postman
- REST Assured (Java)
- SoapUI
- Katalon Studio
- JMeter
- Swagger/OpenAPI
Types of API Testing
- Functional Testing
- Load Testing
- Security Testing
- Reliability Testing
- Negative Testing
- Validation Testing
Best Practices
- Use real data when possible.
- Test for both positive and negative scenarios.
- Automate repetitive test cases.
- Keep authentication and headers modular.
- Validate responses thoroughly — status codes, headers, body.
Pro Tips
- Use Postman collections with environment variables for reusability.
- Integrate API tests in CI/CD pipelines.
- Version your API and test each version independently.
- Monitor APIs in production using tools like New Relic or Datadog.