How to set up already consistent data for Google App Engine unit tests?

I know that App Engine datastore queries are only eventually consistent. However, for some of my tests, I would like to seed the datastore with already consistent data (i.e. it was saved a long time before the test occurred and is now globally consistent).

What is the best way to do this?

I'm using Google Cloud Endpoints for Java, but I'm not anything specific to Endpoints here.