GCS Mock API to use for local development

[morpheus]

I am working on a project in which I would be using GCS to storage data in production. However, when developing locally I am not able to use the real GCS because I don't have the credentials and various other reasons. Is there a recommended best practice here and a mock API to use with local development? I don't want a completely mock API because I do need to be able to retrieve the data. I found this

Is this the right thing I am looking for or is there a better alternative and best practice like using a separate test project? Separate project adds to project costs and increased overhead.