Topic: Unit Testing vs Integration Testing

Unit Testing
  • Focuses on testing individual components such as functions, classes, or methods.
  • Ensures each piece of code works correctly in isolation.
  • Commonly automated with frameworks like JUnit, TestNG, NUnit, or PyTest.
Example
  • Testing a method that calculates the total price of items in a shopping cart.
Integration Testing
  • Focuses on testing interactions between components or systems.
  • Ensures that modules work together correctly after integration.
  • Can be executed using approaches such as Postman or Selenium alongside test frameworks.
  • Types of integration testing:
    • Big Bang: integrate all modules at once and test the combined system.
    • Incremental: integrate and test step by step, including Top-Down, Bottom-Up, and Sandwich strategies.
Example
  • Testing how the shopping cart module interacts with the payment gateway module.
Key Differences
Side-by-side comparison of unit testing and integration testing
Aspect Unit Testing Integration Testing
Scope Individual functions or modules Interaction between modules
Performed By Developers (mostly) Developers and testers
Tools JUnit, TestNG, NUnit, PyTest Postman, Selenium, JUnit/TestNG (integration setups)
Goal Ensure correctness of each small unit Ensure modules work together
Execution Stage Early during coding After unit tests and before system testing
Why Both Are Important
  • Unit testing catches bugs early in small pieces of code.
  • Integration testing confirms those units work correctly when combined.
  • Running both reduces defect leakage to higher testing phases.