Integration Testing

Integration Testing is the testing of interactions between integrated modules or components to verify that they work together as expected.

Integration testing answers: “Do the combined units communicate and function correctly?”

1. Definition

Integration Testing is the testing of interactions between integrated modules or components to verify that they work together as expected.

Integration testing answers: “Do the combined units communicate and function correctly?”

2. Purpose of Integration Testing

• Detect interface defects between modules
• Validate data flow across components
• Ensure correct interaction between systems
• Identify issues not visible in unit testing

3. What Is Integrated in Integration Testing

• Module-to-module integration
• Frontend-to-backend integration
• Application-to-database interaction
• Application-to-external systems (APIs, services)

4. Types of Integration Testing (Conceptual)

4.1 Big Bang Integration

• All modules integrated at once
• Testing starts after full integration
• Risk: Hard to isolate defects

4.2 Incremental Integration

• Modules integrated gradually
• Types:
  • Top-Down
  • Bottom-Up
  • Hybrid
• Advantage: Easier defect isolation

5. Manual Tester’s Role in Integration Testing

• Validate data passed between modules
• Verify correct sequence of operations
• Check error handling between components
• Test positive and negative integration scenarios

6. Integration Testing vs Unit Testing

7. Common Integration Defects

• Incorrect data mapping
• Interface mismatch
• Broken API contracts
• Improper error handling
• Dependency failures

8. Real-Time Example

Login module integration:

• UI → Authentication service
• Authentication → Database
• Authentication → Email service

Integration testing ensures all these connections work together.

9. Entry & Exit Criteria (Integration Testing)

Entry Criteria

• Units tested successfully
• Integrated modules available
• Test environment ready

Exit Criteria

• Critical integration defects resolved
• Data flow validated
• Integration scenarios executed

10. Common Mistakes

• Skipping integration testing
• Testing only happy paths
• Ignoring negative integration scenarios
• Poor coordination with developers

11. Interview-Ready Answers

Short answer:

Integration testing verifies the interaction and data flow between integrated modules or components.

Detailed answer:

Integration testing ensures that combined units work together correctly by validating interfaces, data exchange, and error handling between modules.

12. Key Takeaway

Integration Testing catches interaction defects early, before they impact the full system.