add async_logger tests

cover discarded messages use-case

tests/async_logger.cpp

@@ -0,0 +1,38 @@
+
+#include <iostream>
+
+#include "includes.h"
+#include "../include/spdlog/common.h"
+#include "../include/spdlog/tweakme.h"
+
+
+TEST_CASE("async_logging_overflow ", "[async_logging]")
+{
+	std::string filename = "logs/async_log_overflow.txt";
+	auto sink = std::make_shared<spdlog::sinks::simple_file_sink_st>(filename, true);
+	auto logger = std::make_shared<spdlog::async_logger>(
+		"overflow_logger", 
+		sink,
+		2, // queue size
+		spdlog::async_overflow_policy::discard_log_msg
+	);
+	for (int i = 0; i < 8; i++) {
+		logger->info("Message #{}", i);
+	}
+	logger->flush();
+	logger.reset();
+	std::string the_log = file_contents(filename);
+#if defined(SPDLOG_ASYNC_COUNT_DISCARDED_MSG)
+	std::cout << the_log << std::endl;
+	REQUIRE(the_log.find("Dropped 6 messages") != std::string::npos);
+#endif
+}
+
+
+
+
+
+
+
+
+