Add -Werror to tests

test/CMakeLists.txt

@@ -84,6 +84,9 @@ function(add_fmt_test name)
   if (FMT_PEDANTIC)
     target_compile_options(${name} PRIVATE ${PEDANTIC_COMPILE_FLAGS})
   endif ()
+  if (FMT_WERROR)
+    target_compile_options(${name} PRIVATE ${WERROR_FLAG})
+  endif ()
   target_include_directories(${name} SYSTEM PUBLIC gtest gmock)
   add_test(NAME ${name} COMMAND ${name})
 endfunction()