build unit tests with catch2

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "Catch2"]
+	path = Catch2
+	url = https://github.com/catchorg/Catch2

CMakeLists.txt

@@ -1,7 +1,15 @@
 cmake_minimum_required (VERSION 3.10)
 project (CppLogger)
 
-# Using Catch2's benchmarking tools
-set(CATCH_HEADER_FILES Logger.hpp Singleton_DCLP.hpp ArgParser.hpp)
+option(BUILD_TESTS "Build unit tests with Catch2" OFF)
+
+set(HEADER_FILES Logger.hpp Singleton_DCLP.hpp ArgParser.hpp)
 add_executable(cpplogger main.cpp ${HEADER_FILES})
 set_target_properties(cpplogger PROPERTIES COMPILE_FLAGS "-ggdb")
+
+if (BUILD_TESTS)
+	set(CATCH_HEADER_FILE Catch2/single_include/catch2/catch.hpp)
+	add_executable(cpplogger_test cpp_logger_test.cpp ${HEADER_FILES} ${CATCH_HEADER_FILE})
+	target_include_directories(cpplogger_test PRIVATE . Catch2/single_include)
+	set_target_properties(cpplogger_test PROPERTIES COMPILE_FLAGS "-ggdb")
+endif()

Catch2

@@ -0,0 +1 @@
+Subproject commit 930f49a641aa6a495d264d7b5e7c007734da0b0c

cpp_logger_test.cpp

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+// Let Catch provide main():
+#define CATCH_CONFIG_MAIN
+// #define CATCH_CONFIG_ENABLE_BENCHMARKING
+
+#include <sstream>
+
+#include <catch2/catch.hpp>
+
+#include <Logger.hpp>
+
+
+TEST_CASE( "Simple test" ) {
+
+	// setup
+	std::ostringstream oss;
+	Logger::getInstance()->setStream(&oss);
+
+
+	// simple usage
+	LOG  << "pretty weather" << END;
+	REQUIRE( oss.str() == "pretty weather\n" );
+
+	// chaining inserts
+	oss.str("");
+	const std::string s = "apple(s)";
+	const int i = 2;
+	LOG << "i have " << i << " " << s << END;
+	REQUIRE( oss.str() == "i have 2 apple(s)\n" );
+
+	// output is only written at END
+	oss.str("");
+	LOG  << 1;
+	LOG  << 2;
+	REQUIRE( oss.str() == "" );
+	LOG << END;
+	REQUIRE( oss.str() == "12\n" );
+	LOG  << 3;
+	REQUIRE( oss.str() == "12\n" );
+
+	oss.str("");
+	LOG << END;
+	REQUIRE( oss.str() == "3\n" );
+}
+