For the purpose of testing, I would like to mock Cloud Storage because it slows tests down.
Is there Google Cloud Storage emulator?
There isn't an official emulator provided by Google for the time being.
I'm currently using project Minio (https://www.minio.io/) for mocking Google Storage's behavior in development (Minio uses the filesystem as storage backend and provides compatibility with S3 apiV2, which is compatible with Google Storage).