CMakeLists.txt: use FetchContent to add Catch2 as dependency

Author: dvsav

build/CMake/CMakeLists.txt

@@ -64,6 +64,26 @@ endforeach()
 # Defines a build target - the executable file and its dependencies (the source files collected above)
 add_executable(${PROJECT_NAME} ${SOURCE_FILES})
 
+# Include CMake's FetchContent module
+include(FetchContent)
+
+# Add a dependency: unit testing framework Catch2
+# (https://github.com/catchorg/Catch2/blob/devel/docs/cmake-integration.md)
+
+# FetchContent_Declare declares where and how to fetch the content (e.g., Git URL, tarball, local path), but does not yet download or unpack it.
+FetchContent_Declare(
+    Catch2
+    GIT_REPOSITORY https://github.com/catchorg/Catch2.git
+    GIT_TAG v3.8.1)
+# FetchContent_MakeAvailable does the following:
+# 1. Download or copy the external content to a local directory (<binary_dir>/_deps/ by default).
+# 2. Extract/unpack it if it's an archive.
+# 3. Prepare it for inclusion in the build (e.g., by configuring it).
+# This step is what CMake refers to as "populating the content" — turning the declaration into actual usable files.
+FetchContent_MakeAvailable(Catch2)
+# Link to the Catch2 static library
+target_link_libraries(${PROJECT_NAME} PRIVATE Catch2::Catch2WithMain)
+
 if (VISUAL_STUDIO)
     # set our project as the startup project in the Visual Studio solution
     set_property(

build/GNUMake/Makefile

@@ -50,6 +50,10 @@ ifeq ($(findstring CYGWIN,$(UNAME)),CYGWIN)
 	CXXFLAGS+=-Wa,-mbig-obj
 endif
 
+# Define CATCH2_SINGLE_HEADER macrodefinition to use the single-header
+# version of Catch2 unit testing framework (the macrodefinition is used in test.cpp file)
+CXXFLAGS+=-DCATCH2_SINGLE_HEADER
+
 # Linking to libstdc++fs is required for use of the Filesystem library extensions in <experimental/filesystem>
 STDLIBS= \
     -lstdc++fs

src/test.cpp

@@ -27,9 +27,15 @@
 
 #include "nlohmann/json.hpp"  // JSON parser
 
-// Catch2 - a single header unit test framework
-#define CATCH_CONFIG_MAIN  // This tells Catch to provide a main() - only do this in one cpp file
-#include "Catch2/catch.hpp"
+// Catch2 - unit testing framework
+#ifdef CATCH2_SINGLE_HEADER
+    // Use the single header version of Catch2
+    #define CATCH_CONFIG_MAIN  // This tells Catch to provide a main() - only do this in one cpp file
+    #include "Catch2/catch.hpp"
+#else
+    // Use the static library version of Catch2
+    #include <catch2/catch_test_macros.hpp>
+#endif
 
 TEST_CASE("Karatsuba", "[karatsuba]")
 {