In the repository-gcs plugin, many tests rely on the GoogleCloudServer utility class to simulate calls to the Google Cloud Storage API.

While GoogleCloudServer is really useful in fixtures like GoogleCloudStorageFixture, it would be better if the following test classes use a more pure unit testing mock for the service calls inside the unit tests:

• GoogleCloudStorageBlobStoreContainerTests
• GoogleCloudStorageBlobStoreRepositoryTests
• GoogleCloudStorageBlobStoreTests

Related to #28788 (comment)