What is integrationtest?

An integration test is a type of software test that checks how different parts of an application work together. Instead of testing a single function or module in isolation (unit testing), integration testing combines those pieces to see if they communicate correctly, share data properly, and produce the expected overall behavior.

Let's break it down

  • Units: Small, individual pieces of code (functions, classes, modules).
  • Integration: Putting two or more units together.
  • Test: Running the combined code with specific inputs and checking the outputs. In an integration test you set up a realistic scenario, call the combined components, and verify the result matches what the whole system should do.

Why does it matter?

  • Find hidden bugs: Issues often appear only when components interact, such as mismatched data formats or incorrect API calls.
  • Confidence: Shows that the system works as a whole, not just as isolated parts.
  • Early detection: Catches problems before they reach production, saving time and money.

Where is it used?

  • Web applications: Testing how the front‑end talks to the back‑end API and database.
  • Microservices: Verifying that separate services can call each other correctly.
  • Mobile apps: Checking interaction between UI, local storage, and remote services.
  • Embedded systems: Ensuring hardware drivers and software layers cooperate.

Good things about it

  • Catches integration‑level bugs that unit tests miss.
  • Provides a realistic view of how the system behaves in real use.
  • Helps validate contracts (e.g., API request/response formats).
  • Can be automated and run in continuous integration pipelines.

Not-so-good things

  • Slower to run than unit tests because they often involve databases, networks, or external services.
  • More complex to set up and maintain (need test data, mock services, environment configuration).
  • Can be flaky if external dependencies are unstable, leading to false failures.
  • May require more effort to isolate the cause of a failure compared to unit tests.