Catch2 / Google Test for C++: Complete Guide with Examples

Introduction: What are Catch2 and Google Test and why are they needed?

In modern C++ software development, testing is not a luxury but a necessity. Unit testing libraries allow developers to automatically verify that individual program components (functions, classes, modules) work correctly. The two most popular libraries for this purpose are Catch2 and Google Test (gtest).

Catch2 is a modern, lightweight, and very convenient unit testing library. Its main feature is the use of macros that make tests readable and resemble plain English. Catch2 supports the Behaviour-Driven Development (BDD) style, automatic test registration, and does not require complex configuration.

Google Test (gtest) is a powerful and mature library from Google that is the de facto standard in many large projects. It offers a rich set of assertion macros, mechanisms for creating test fixtures, parameterized tests, and excellent integration with the CMake build system.

Both libraries solve the same problem: they allow you to write tests that run automatically and report results. The choice between them often depends on personal preferences, project requirements, or existing infrastructure. In this article, we will look at both libraries, as they are very similar in concept but have differences in syntax and API.

Installation

Unlike Python (where pip is used), installing libraries for C++ usually happens through system package managers or through integration with a build system (e.g., CMake). Let's look at both options.

Installing Catch2

Method 1: Via vcpkg (recommended)

# Install vcpkg if not already installedgit clone https://github.com/Microsoft/vcpkg.gitcd vcpkg./bootstrap-vcpkg.sh  # or .\\bootstrap-vcpkg.bat on Windows

# Install Catch2./vcpkg install catch2

# Integration with CMake./vcpkg integrate install

Method 2: Header-only (simplest)
Catch2 can be used as a header-only library. Simply download the catch.hpp file from the official repository and place it in your project folder. Then include it in your code:

#define CATCH_CONFIG_MAIN  // This line should be in only one .cpp file#include "catch.hpp"

Installing Google Test

Method 1: Via vcpkg

./vcpkg install gtest./vcpkg integrate install

Method 2: Via CMake FetchContent (recommended for CMake projects)
Add to your CMakeLists.txt:

include(FetchContent)FetchContent_Declare(  googletest  GIT_REPOSITORY https://github.com/google/googletest.git  GIT_TAG release-1.12.1)FetchContent_MakeAvailable(googletest)

# Now you can use target_link_libraries for your test fileadd_executable(my_tests test.cpp)target_link_libraries(my_tests GTest::gtest_main)

Quick Start with Code Example

Let's write a simple function and test it using both libraries. The function will calculate the factorial of a number.

Example with Catch2

#define CATCH_CONFIG_MAIN#include "catch.hpp"

// Function to testunsigned int factorial(unsigned int n) {    if (n == 0) return 1;    return n * factorial(n - 1);}

// Test caseTEST_CASE("Factorials are computed correctly", "[factorial]") {    REQUIRE(factorial(0) == 1);    REQUIRE(factorial(1) == 1);    REQUIRE(factorial(2) == 2);    REQUIRE(factorial(3) == 6);    REQUIRE(factorial(10) == 3628800);}

// Another test case with sectionsTEST_CASE("Checking edge cases", "[factorial][edge]") {    SECTIO