What is an integration test?

• A. A test that verifies a small part of code in isolation.
• B. Checks how combined parts of a system work together.
• C. A test that checks system performance when overloaded.
• D. A test that validates the user interface layout.

Answer: (B)

Integration testing focuses on how different parts of a system work together. It checks that interfaces between modules are correct, data flows properly, and the combined behavior matches expectations when the parts interact. This usually comes after unit testing, which validates individual components in isolation, and before system testing that looks at the entire end-to-end experience. For example, you’d test that the order processing module properly communicates with inventory and payment services, sending the right data and handling responses correctly. This distinguishes it from tests that target a single function by itself, performance tests that push the system under load, or tests that verify how the user interface is laid out.