Testing with Catch2

We have seen how assert() can help catch logic errors during development, but it has an important limitation: the program terminates immediately when the first assertion fails. In larger projects, this is impractical. We often need to validate dozens or hundreds of behaviors in a single run and receive a complete report showing which tests passed and which failed, without halting execution at the first error.

This is where unit testing frameworks come in. A unit testing framework allows us to define many independent tests, execute them all in one run, and collect detailed feedback about failures.

In this lesson, we will introduce Catch2, a modern, widely used C++ testing framework. Catch2 enables us to write expressive, readable tests using simple C++ syntax, making systematic testing a natural part of the development workflow rather than an afterthought.

Beyond simple assertions

Using assert() amounts to ad-hoc testing. When an assertion fails, program execution stops immediately, preventing any subsequent checks from running. This is analogous to a teacher halting the grading of an exam after encountering the first incorrect answer, useful for catching an error but inefficient for assessing overall correctness. Professional software development requires structured testing. A dedicated testing framework provides several key advantages:

• Test isolation:
  Each test is executed independently. A failure in one test does not prevent others from running.

• Clear reporting:
  The framework reports precisely which tests failed and includes detailed information ...