How can we cover unit testing for datastore?

Right now, the only way to develop this is by hitting the live Cloud Datastore API. Is there a way we can use these API calls in unit tests without mocking?

Can we have a "local datastore" server that understands the API and makes it easy for local development?

You could use gcd: the local development server, see:
https://developers.google.com/datastore/docs/tools/devserver

That looks good for local development. It runs on Java right ?

I wonder how difficult it would be to patch in the stubs from AppEngine's dev_appserver.py so that i can use something akin to ext.testbed to unittest locally (ie, without hitting the wire, stay all in Python).

That looks good for local development. It runs on Java right ?

Yes, it is embedding the App Engine Java development server and running the same servlet that is running in production.

I wonder how difficult it would be to patch in the stubs from AppEngine's dev_appserver.py so that i can use something akin to ext.testbed to unittest locally (ie, without hitting the wire, stay all in Python).

You would have to handle the datastore_v1.proto to datastore_v4 convertion somehow.

Keep in mind that datastore_v4 private interface is not really documented and also subject to change: datastore_v1 is the public versionned interface.

Yikes. Well I realllly don't want to force people to spin up a local server in order to run unit tests...

We'll have to come up with a way to stub this out.

#130 adds 100% unit test coverage for modules in gcloud, gcloud.datastore. I would call its strategy "stubbing" (testcases explicitly stub out the http or connection objects) rather than "mocking" (using a general-purpose utilitiy like 'mock').