googletest/googlemock/g3doc/includes/g3_mock_multithreaded.md

Can I use gMock in multi-threaded programs?

googletest was designed with thread-safety in mind. It uses synchronization primitives from google3 to be thread-safe. If you work in google3, you can use gMock in multiple threads safely. If you work outside of google3 and need gMock to be thread-safe, please let us know.

For more details on how to use gMock with threads, read this recipe.