fake-gcs-server provides an emulator for Google Cloud Storage API. It can be used as a library in Go projects and/or as a standalone binary/Docker image.

The library is available inside the package github.com/fsouza/fake-gcs-server/fakestorage and can be used from within test suites in Go package. The emulator is available as a binary that can be built manually, downloaded from the releases page or pulled from Docker Hub (docker pull fsouza/fake-gcs-server).

You can stub/mock Google Cloud Storage as a standalone server (like the datastore/pubsub emulators) which is ideal for integration tests and/or tests in other languages you may want to run the fake-gcs-server inside a Docker container:

docker run -d --name fake-gcs-server -p 4443:4443 fsouza/fake-gcs-server

In case you want to preload some data in fake-gcs-server just mount a folder in the container at /data:

docker run -d --name fake-gcs-server -p 4443:4443 -v ${PWD}/examples/data:/data fsouza/fake-gcs-server

Where the content of ${PWD}/examples/data is something like:

.
└── sample-bucket
    └── some_file.txt

To make sure everything works as expected you can execute these commands:

curl --insecure https://0.0.0.0:4443/storage/v1/b
{"kind":"storage#buckets","items":[{"kind":"storage#bucket","id":"sample-bucket","name":"sample-bucket"}],"prefixes":null}

curl --insecure https://0.0.0.0:4443/storage/v1/b/sample-bucket/o
{"kind":"storage#objects","items":[{"kind":"storage#object","name":"some_file.txt","id":"sample-bucket/some_file.txt","bucket":"sample-bucket","size":"33"}],"prefixes":[]}

This will result in one bucket called sample-bucket containing one object called some_file.txt.

fake-gcs-server defaults to HTTPS, but it can also be used with HTTP. The flag -scheme can be used to specify the protocol. For example, the previous example could be changed to pass -scheme http:

docker run -d --name fake-gcs-server -p 4443:4443 -v ${PWD}/examples/data:/data fsouza/fake-gcs-server -scheme http

And now we can curl it without the --insecure flag and using https:// instead of https://:

curl https://0.0.0.0:4443/storage/v1/b
{"kind":"storage#buckets","items":[{"kind":"storage#bucket","id":"sample-bucket","name":"sample-bucket"}],"prefixes":null}

curl https://0.0.0.0:4443/storage/v1/b/sample-bucket/o
{"kind":"storage#objects","items":[{"kind":"storage#object","name":"some_file.txt","id":"sample-bucket/some_file.txt","bucket":"sample-bucket","size":"33"}],"prefixes":[]}

It is possible to use fake-gcs-server with signed URLs, although with a few caveats:

• No validation is made on the query params (signature, expiration ...)
• You need your client to modify the URL before passing it around (replace storage.googleapis.com with something that points to fake-gcs-server)
• You need to configure fake-gcs-server to accept this local URL (by setting -public-host)

fake-gcs-server supports various features that can be configured through flags upon start. Use the -help flag to list all of them alongside their usage instructions

docker run --rm fsouza/fake-gcs-server -help

For examples using SDK from multiple languages, check out the examples directory.

You may use docker build to build the image locally instead of pulling it from Docker Hub:

docker build -t fsouza/fake-gcs-server .