I'm trying to write a plugin at the moment (datasette-atom) which needs to run unit tests against a full in-memory Datasette instance, in the same way that the Datasette test suite itself works.

I got it working by creating copies of the TestClient and TestResponse classes within the plugin itself:

simonw/datasette-atom@c0e3bd9#diff-33337525d2d877f7cc7f33737bfd2d7b

I had to do this because those classes are in the tests/ directory within Datasette, so they don't get included in the package that ships to PyPI.

It would be better if these classes were included in the main package in a way that made it easy for plugins to reuse them to write their own tests.