Fix include order

tests/CMakeLists.txt

@@ -1,6 +1,7 @@
 include_directories(${PROJECT_SOURCE_DIR}/include)
 include_directories(${PROJECT_SOURCE_DIR}/deps)
 include_directories(${PROJECT_SOURCE_DIR}/src)
+include_directories(${PROJECT_SOURCE_DIR}/src_extra)
 include_directories(${PROJECT_BINARY_DIR}/src_generated)
 
 find_package(Check REQUIRED)