We currently have two types of query test classes: classes which inherit from QueryTestBase, where a single model is shared across all tests, and non-shared (ad-hoc) tests, where each test creates its own model. This leads to a situation where the same "area" frequently has two test classes, e.g. JsonQuerySqlServerTest and AdHocJsonQuerySqlServerTest.

We could consider simply allowing non-shared tests inside regular QueryTestBase test classes; this would reduce the overall number of test classes, it would concentrate all the tests relating to a given area in a single class, we'd be able to put related tests next to each other, etc. Tests using non-shared models would automatically use a separate database (whose name could be derived from the shared-model one, e.g. by tacking on "NonShared").

One theoretical downside is that we would no longer parallelize pairs of shared and non-shared tests as we do now, but given the overall number of tests and classes we have, that seems to be really negligible.

/cc @maumar