GSMock is a mocking utility for the Google Search Appliance. It enables search responses to be mocked for search requests.
GSMock was created from the scenario where I found myself creating applications which needed to integrate with a GSA, however I had no GSA to develop or test with.
GSMock is essentially a request handler with xml configuration allowing static files to be configured for collection data, and xslt for front-end transformations.
For getting started, please refer to the documentation