Update patch file

Signed-off-by: Jorge Perez <jjperez@ekumenlabs.com>

rcl/test/mocking_utils/patch.hpp

@@ -332,15 +332,29 @@ auto make_patch(const std::string & target, std::function<SignatureT> proxy)
 #define MOCKING_UTILS_PATCH_TARGET(scope, function) \
   (std::string(RCUTILS_STRINGIFY(function)) + "@" + (scope))
 
-/// Patch a `function` with a used-provided `replacement` in a given `scope`.
-#define patch(scope, function, replacement) \
+/// Prepare a mocking_utils::Patch for patching a `function` in a given `scope`
+/// but defer applying any changes.
+#define prepare_patch(scope, function) \
   make_patch<__COUNTER__, decltype(function)>( \
     MOCKING_UTILS_PATCH_TARGET(scope, function), MOCKING_UTILS_PATCH_PROXY(function) \
-  ).then_call(replacement)
+  )
 
-/// Patch a function with a function that only returns a value
-#define patch_and_return(scope, function, return_value) \
-  patch(scope, function, [&](auto && ...) {return return_value;})
+/// Patch a `function` with a used-provided `replacement` in a given `scope`.
+#define patch(scope, function, replacement) \
+  prepare_patch(scope, function).then_call(replacement)
+
+/// Patch a `function` to always yield a given `return_code` in a given `scope`.
+#define patch_and_return(scope, function, return_code) \
+  patch(scope, function, [&](auto && ...) {return return_code;})
+
+/// Patch a `function` to execute normally but always yield a given `return_code`
+/// in a given `scope`.
+#define inject_on_return(scope, function, return_code) \
+  patch( \
+    scope, function, ([&, base = function](auto && ... __args) { \
+      static_cast<void>(base(std::forward<decltype(__args)>(__args)...)); \
+      return return_code; \
+    }))
 
 }  // namespace mocking_utils