testing system function override

tests/test_system_function.cpp

@@ -0,0 +1,25 @@
+// Copyright (c) Lysann Tranvouez.  All rights reserved.
+
+#include <catch2/catch_test_macros.hpp>
+
+#include <mach_detours.h>
+
+char* (*realStrerror)(int) = strerror;
+char* strerrorDetour(int errno)
+{
+    return (char *)"strerrorOverride";
+}
+
+TEST_CASE( "Overriding system function", "[attach][system]" )
+{
+    REQUIRE( std::string_view(strerror( 0 )) == "Undefined error: 0" );
+
+    REQUIRE( detour_transaction_begin() == err_none );
+    REQUIRE( detour_attach_and_commit(reinterpret_cast<detour_func_t*>(&realStrerror), reinterpret_cast<detour_func_t>(strerrorDetour)) == err_none );
+
+    CHECK( std::string_view(strerror( 0 )) == "strerrorOverride" );
+
+    // clean up
+    CHECK( detour_transaction_begin() == err_none );
+    CHECK( detour_detach_and_commit(reinterpret_cast<detour_func_t*>(&realStrerror), reinterpret_cast<detour_func_t>(strerrorDetour)) == err_none );
+}