Integration tests are checks to see if different parts of a program work well together. Instead of testing one small piece alone, they test how pieces connect and share data.

How it works

A program might have many modules - like login, database, and payment. Each module can pass its own unit test. But when you connect them, mistakes can appear, like wrong data being sent or features not lining up. Integration tests run real scenarios that involve several modules at once to catch those problems.

Analogy

It's like building a car. You already tested the engine, brakes, and wheels separately. Now you put them together and check if pressing the brake actually slows down the moving car. That combined check is the integration test.