From 5d833e2928dce9694a846d6e787c7721a6c9e170 Mon Sep 17 00:00:00 2001
From: Lysann Tranvouez <lysann.tranvouez@gmail.com>
Date: Thu, 2 Oct 2025 22:41:33 +0200
Subject: [PATCH] testing system function override

---
 tests/CMakeLists.txt           |  1 +
 tests/test_dylib_function.cpp  |  2 +-
 tests/test_local_function.cpp  |  2 +-
 tests/test_system_function.cpp | 25 +++++++++++++++++++++++++
 4 files changed, 28 insertions(+), 2 deletions(-)
 create mode 100644 tests/test_system_function.cpp

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index f9cc485..17c8a60 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -3,6 +3,7 @@
 add_executable(mach_detours_tests
         test_dylib_function.cpp
         test_local_function.cpp
+        test_system_function.cpp
         test_transaction.cpp
 )
 
diff --git a/tests/test_dylib_function.cpp b/tests/test_dylib_function.cpp
index c32679a..4ad66cb 100644
--- a/tests/test_dylib_function.cpp
+++ b/tests/test_dylib_function.cpp
@@ -14,7 +14,7 @@ static int libFunctionDetour()
     return 94;
 }
 
-TEST_CASE( "Overriding custom function in dylib", "[dylib]" )
+TEST_CASE( "Overriding custom function in dylib", "[attach][detach][dylib]" )
 {
     libFunctionCounter = 0;
     libFunctionDetourCounter = 0;
diff --git a/tests/test_local_function.cpp b/tests/test_local_function.cpp
index 97af062..49b2d60 100644
--- a/tests/test_local_function.cpp
+++ b/tests/test_local_function.cpp
@@ -18,7 +18,7 @@ int localFunctionDetour()
     return 12;
 }
 
-TEST_CASE( "Overriding local function", "[local][attach]" )
+TEST_CASE( "Overriding local function", "[attach][local]" )
 {
     localFunctionCounter = 0;
     localFunctionDetourCounter = 0;
diff --git a/tests/test_system_function.cpp b/tests/test_system_function.cpp
new file mode 100644
index 0000000..31b285f
--- /dev/null
+++ b/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 );
+}