🧑‍💻 Integration Testing –

 

1. What is Integration Testing?

Integration testing is about checking how two or more parts of a software work together.

• When developers build software, they split it into different modules (like login, cart, payment).
• First, each module is tested separately (this is unit testing).
• Then in integration testing, we combine modules and check if they talk to each other properly.

👉 Example: In an online shopping app – when a customer adds items to the cart and then goes to payment, integration testing ensures the cart details are correctly passed to the payment page.

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2. Different Ways to Do Integration Testing

• Big Bang Approach: Test everything together at once.
  • Example: Login → Search → Add to Cart → Pay → Invoice (all tested together).
• Top-Down Approach: Start testing from the top-level module and slowly add the lower ones. Use fake programs (called stubs) if the lower modules are not ready.
  • Example: Check Place Order → Payment and use a stub to pretend that delivery service works.
• Bottom-Up Approach: Start testing from the bottom modules (like database and services) and move up. Use fake programs (called drivers) for higher modules.
  • Example: Test Database → Payment Service even if the UI (screen) is not ready, by using a driver to call payment functions.
• Sandwich / Hybrid Approach: Mix of top-down and bottom-up.

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3. How is it Different from Other Testing?

• Unit Testing: Check only one small part (like “login API gives success when username and password are correct”).
• Integration Testing: Check how two or more parts work together (like “login API + database + session management work correctly”).
• System Testing: Check the whole application end-to-end (like “login → dashboard → logout”).

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4. Examples of Integration Testing

Banking App Example – Fund Transfer

• Modules: Account Balance, Fund Transfer, Notification
• Test Case:
  1. Transfer ₹5,000 from Account A to Account B.
  2. Account A balance should reduce.
  3. Account B balance should increase.
  4. SMS notification should be sent.

Shopping App Example – Place Order

• Modules: Product Selection, Cart, Payment, Invoice
• Test Case:
  1. Add product to cart.
  2. Go to checkout and make payment.
  3. Payment success → Invoice generated.
  4. Cart should become empty.

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5. How Can You Do Integration Testing?

• Manually: Write test cases and test step by step. If some modules are not ready, use stubs (fake lower modules) or drivers (fake higher modules).
• With Tools:
  • API Testing: Postman, REST Assured (Java), PyTest + Requests (Python).
  • UI Testing: Selenium, Cypress.
  • Automation with CI/CD: Jenkins, GitHub Actions.

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6. Tips / Best Practices

• Always start with important data flow paths (like money transfer or checkout).
• If a module is not ready, use stubs/drivers to simulate it.
• Automate API-level tests because they are faster and more stable than UI tests.
• Use real-looking test data (e.g., valid account numbers, valid product IDs).
• Keep track of which modules are dependent on which.

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✅ In Short: Integration Testing = making sure modules work properly together. Without it, software may pass unit tests but fail in real-world usage.

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Now you have a clear idea of what integration testing is.  Explore other topics of Manual testing