Testing utilities should be available to plugins

[simonw]

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.

[simonw]

I needed this again today for datasette-template-sql.

[simonw]

One thing that would be useful is a way of constructing a Datasette() instance (and accompanying TestClient) which is attached to an in-memory database that the test itself can manipulate. This would make it trivial to run tests against hypothetical database tables - those tables could be created using sqlite-utils directly against the in-memory database that's being manipulated by the system-under-test.

[simonw]

Here's where I copied the testing utilities into datasette-template-sql - very slightly modified from the utilities in datasette-atom: https://github.com/simonw/datasette-template-sql/blob/0ef0c7304bb5e658723e229d3ee463b9a76058f9/tests/utils.py

[simonw]

datasette-atom shipped with a copy of these classes too: https://github.com/simonw/datasette-atom/blob/c2e84207fccff0582d7152f3966dd2952fb0b74f/tests/utils.py

[simonw]

I don't think this is needed any more - I've found a really nice pattern for testing plugins using httpx instead, e.g. https://github.com/simonw/datasette-mask-columns/blob/f6f08ce21bdfc2731a02c42e1c9e25b4df769292/tests/test_mask_columns.py