Develop C++ unit testing with Catch2, JUnit, and GitLab CI

This post introduces the integration of Catch2 unit testing into a C++ application and its subsequent setup within GitLab CI. It details project structuring for testability, including separating application logic into header and source files, and configuring CMake to build both the application and its tests. The post also demonstrates writing basic tests using Catch2 macros and assertions, and outlines the CI pipeline configuration to compile and run these tests.