Add tests to verify std::function works with capturing lambda

Introduce a test that uses a capturing lambda as a custom_fake.

Signed-off-by: Yuval Peress <peress@google.com>

test/CMakeLists.txt

@@ -38,6 +38,22 @@ add_executable(cpp_global_test
 target_include_directories(cpp_global_test PRIVATE include)
 target_link_libraries(cpp_global_test PRIVATE gtest fff)
 
+# Create the C++ custom function signature executable
+add_executable(cpp_custom_fn_signature_test
+    src/fff_test_custom_function_template.cpp
+    ${COMMON_FILE_LIST}
+)
+target_include_directories(cpp_custom_fn_signature_test PRIVATE include)
+target_link_libraries(cpp_custom_fn_signature_test PRIVATE gtest fff)
+# Due to a bug in WinLibs for Windows it's not currently possible to use:
+#   target_precompile_headers(cpp_custom_fn_signature_test PUBLIC include/custom_function.hpp)
+# See more info at target_precompile_headers(cpp_custom_fn_signature_test PUBLIC include/custom_function.hpp)
+
+add_test(
+      NAME cpp_custom_fn_signature_test
+      COMMAND $<TARGET_FILE:cpp_custom_fn_signature_test>
+  )
+
 # Add the tests for ctest
 add_test(
     NAME c_test

test/include/custom_function.hpp

@@ -0,0 +1,10 @@
+/* Copyright 2022 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+#include <functional>
+
+#define CUSTOM_FFF_FUNCTION_TEMPLATE(RETURN, FUNCNAME, ...) \
+    std::function<RETURN (__VA_ARGS__)> FUNCNAME

test/include/fff_wrapper.hpp

@@ -0,0 +1,11 @@
+/* Copyright 2022 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+#include <functional>
+
+#include "custom_function.hpp"
+
+#include <fff.h>

test/src/fff_test_custom_function_template.cpp

@@ -0,0 +1,29 @@
+/* Copyright 2022 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <gtest/gtest.h>
+
+#include "fff_wrapper.hpp"
+
+DEFINE_FFF_GLOBALS
+
+FAKE_VOID_FUNC(do_stuff, int);
+
+class FFFCustomFakeSuite : public ::testing::Test {
+ public:
+  void SetUp() override {
+    RESET_FAKE(do_stuff);
+    FFF_RESET_HISTORY();
+  }
+};
+
+TEST_F(FFFCustomFakeSuite, custom_cpp_fake_function)
+{
+  int x = 0;
+  do_stuff_fake.custom_fake = [&x](int i) {
+    x = i;
+  };
+  do_stuff(5);
+  ASSERT_EQ(5, x);
+}