diff --git a/external/toxcore/CMakeLists.txt b/external/toxcore/CMakeLists.txt
index fc61af11..d31e082b 100644
--- a/external/toxcore/CMakeLists.txt
+++ b/external/toxcore/CMakeLists.txt
@@ -203,6 +203,10 @@ add_executable(DHT_Bootstrap EXCLUDE_FROM_ALL
 	${TOX_DIR}testing/misc_tools.h
 	${TOX_DIR}testing/misc_tools.c
 )
-
 target_link_libraries(DHT_Bootstrap toxcore)
 
+add_executable(mono_time_test
+	./mono_time_test.cc
+)
+target_link_libraries(mono_time_test toxcore)
+
diff --git a/external/toxcore/mono_time_test.cc b/external/toxcore/mono_time_test.cc
new file mode 100644
index 00000000..754f6db5
--- /dev/null
+++ b/external/toxcore/mono_time_test.cc
@@ -0,0 +1,138 @@
+#include "./c-toxcore/toxcore/mono_time.h"
+
+#ifdef NDEBUG
+	#undef NDEBUG
+	#include <cassert>
+#else
+	#include <cassert>
+#endif
+
+#include <iostream>
+#include <thread>
+#include <chrono>
+
+#define TEST(x, y) bool run_test_##x##y(void)
+
+#define ASSERT_NE(x, y) assert((x) != (y))
+#define EXPECT_GT(x, y) assert((x) > (y))
+#define EXPECT_FALSE(x) assert(!(x))
+#define EXPECT_TRUE(x) assert((x))
+#define EXPECT_EQ(x, y) assert((x) == (y))
+
+TEST(MonoTime, UnixTimeIncreasesOverTime)
+{
+    const Memory *mem = system_memory();
+    Mono_Time *mono_time = mono_time_new(mem, nullptr, nullptr);
+    ASSERT_NE(mono_time, nullptr);
+
+    mono_time_update(mono_time);
+    uint64_t const start = mono_time_get(mono_time);
+
+    while (start == mono_time_get(mono_time)) {
+        mono_time_update(mono_time);
+    }
+
+    uint64_t const end = mono_time_get(mono_time);
+    EXPECT_GT(end, start);
+
+    mono_time_free(mem, mono_time);
+
+	return true;
+}
+
+TEST(MonoTime, IsTimeout)
+{
+    const Memory *mem = system_memory();
+    Mono_Time *mono_time = mono_time_new(mem, nullptr, nullptr);
+    ASSERT_NE(mono_time, nullptr);
+
+    uint64_t const start = mono_time_get(mono_time);
+    EXPECT_FALSE(mono_time_is_timeout(mono_time, start, 1));
+
+    while (start == mono_time_get(mono_time)) {
+        mono_time_update(mono_time);
+    }
+
+    EXPECT_TRUE(mono_time_is_timeout(mono_time, start, 1));
+
+    mono_time_free(mem, mono_time);
+
+	return true;
+}
+
+TEST(MonoTime, IsTimeoutReal)
+{
+    const Memory *mem = system_memory();
+    Mono_Time *mono_time = mono_time_new(mem, nullptr, nullptr);
+    ASSERT_NE(mono_time, nullptr);
+
+    uint64_t const start = mono_time_get(mono_time);
+    EXPECT_FALSE(mono_time_is_timeout(mono_time, start, 5));
+
+	std::this_thread::sleep_for(std::chrono::milliseconds(100));
+	mono_time_update(mono_time);
+
+	// should still not have timed out (5sec) after sleeping ~20ms
+    EXPECT_FALSE(mono_time_is_timeout(mono_time, start, 5));
+
+    mono_time_free(mem, mono_time);
+
+	return true;
+}
+
+TEST(MonoTime, CustomTime)
+{
+    const Memory *mem = system_memory();
+    Mono_Time *mono_time = mono_time_new(mem, nullptr, nullptr);
+    ASSERT_NE(mono_time, nullptr);
+
+    uint64_t test_time = current_time_monotonic(mono_time) + 42137;
+
+    mono_time_set_current_time_callback(
+        mono_time, [](void *user_data) { return *static_cast<uint64_t *>(user_data); }, &test_time);
+    mono_time_update(mono_time);
+
+    EXPECT_EQ(current_time_monotonic(mono_time), test_time);
+
+    uint64_t const start = mono_time_get(mono_time);
+
+    test_time += 7000;
+
+    mono_time_update(mono_time);
+    EXPECT_EQ(mono_time_get(mono_time) - start, 7);
+
+    EXPECT_EQ(current_time_monotonic(mono_time), test_time);
+
+    mono_time_free(mem, mono_time);
+
+	return true;
+}
+
+int main(int argc, char **argv) {
+	if (!run_test_MonoTimeUnixTimeIncreasesOverTime()) {
+		std::cerr << "MonoTimeUnixTimeIncreasesOverTime() failed\n";
+		return -1;
+	}
+	std::cout << "MonoTimeUnixTimeIncreasesOverTime() succeeded\n";
+
+	if (!run_test_MonoTimeIsTimeout()) {
+		std::cerr << "MonoTimeIsTimeout() failed\n";
+		return -1;
+	}
+	std::cout << "MonoTimeIsTimeout() succeeded\n";
+
+	if (!run_test_MonoTimeIsTimeoutReal()) {
+		std::cerr << "MonoTimeIsTimeoutReal() failed\n";
+		return -1;
+	}
+	std::cout << "MonoTimeIsTimeoutReal() succeeded\n";
+
+	if (!run_test_MonoTimeCustomTime()) {
+		std::cerr << "MonoTimeCustomTime() failed\n";
+		return -1;
+	}
+	std::cout << "MonoTimeCustomTime() succeeded\n";
+
+	return 0;
+}
+