Unit Testing in C++

a) Why is Testing Important?

Unit testing is a crucial aspect of software development. Here's why:

1. Quality Assurance: Unit tests ensure that individual units of code (like functions or methods) work as intended.
2. Regression Detection: When changes are made to the codebase, unit tests can detect if previously working functionality has been broken.
3. Documentation: Tests provide a form of documentation by showcasing how a piece of code is intended to be used.
4. Design: Writing tests can help in designing better and more modular code.
5. Confidence: With a comprehensive suite of tests, developers can make changes with the confidence that they haven't inadvertently introduced bugs.

Example: Imagine you have a function add(int a, int b) that returns the sum of two numbers. A unit test would ensure that add(2, 3) always returns 5.

b) Testing in CMake with CTest

CTest is a testing tool distributed as a part of CMake. It allows you to easily create, manage, and run your tests.

Basic Example:

1. In your CMakeLists.txt, enable testing:

   enable_testing()

2. Add a test executable:

   add_executable(my_test test.cpp)

3. Add the test to CTest:

   add_test(NAME MyTest COMMAND my_test)

4. Build and run tests:

   mkdir build && cd build
   cmake ..
   make
   ctest

Documentation: CTest Documentation

Using FetchContent is a popular way to integrate dependencies directly into a CMake project. Here's how you can integrate Google Test using FetchContent:

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c) Testing in CMake with Google Test

Google Test is a popular C++ testing framework. Here's how you can integrate it with CMake using FetchContent:

1. Installation using FetchContent:

   In your CMakeLists.txt, you can fetch Google Test as follows:

   include(FetchContent)
   
   FetchContent_Declare(
     googletest
     GIT_REPOSITORY https://github.com/google/googletest.git
     GIT_TAG        release-1.10.0
   )
   
   FetchContent_MakeAvailable(googletest)

   This will download, build, and make Google Test available in your project.

2. Integration with CMake:

   After fetching Google Test, you can link against it:

   add_executable(my_gtest test_gtest.cpp)
   target_link_libraries(my_gtest gtest_main)

3. Writing a Test:

   #include <gtest/gtest.h>
   
   TEST(MyTestSuite, MyTestCase) {
       EXPECT_EQ(2 + 3, 5);
   }

   With gtest_main as a linked library, you don't need a main function; Google Test provides one for you.

4. Build and run tests as you would with CTest.

Documentation: Google Test Github Repository