Add tests

Signed-off-by: Slendi <slendi@socopon.com>

CMakeLists.txt

@@ -4,11 +4,13 @@ project(SmathExamples CXX)
 set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+option(BUILD_EXAMPLES "Build example programs" ON)
+option(BUILD_TESTS "Build unit tests" ON)
+
 add_library(smath INTERFACE)
 target_include_directories(smath INTERFACE ${CMAKE_SOURCE_DIR}/include)
 add_library(smath::smath ALIAS smath)
 
-option(BUILD_EXAMPLES "Build example programs" ON)
 if(BUILD_EXAMPLES)
 	file(GLOB EXAMPLE_SOURCES "${CMAKE_SOURCE_DIR}/examples/*.cpp")
 	foreach(EXAMPLE_FILE ${EXAMPLE_SOURCES})
@@ -17,3 +19,26 @@ if(BUILD_EXAMPLES)
 		target_link_libraries(${EXAMPLE_NAME} PRIVATE smath::smath)
 	endforeach()
 endif()
+
+if(BUILD_TESTS)
+	enable_testing()
+
+	include(FetchContent)
+	FetchContent_Declare(
+		googletest
+		URL https://github.com/google/googletest/archive/refs/tags/v1.15.2.zip
+	)
+	set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+	FetchContent_MakeAvailable(googletest)
+
+	file(GLOB TEST_SOURCES "${CMAKE_SOURCE_DIR}/tests/*.cpp")
+
+	add_executable(smath_tests ${TEST_SOURCES})
+	target_link_libraries(smath_tests PRIVATE
+		smath::smath
+		GTest::gtest_main
+	)
+
+	include(GoogleTest)
+	gtest_discover_tests(smath_tests)
+endif()