Write generate tests for v1.0 refactored models/generators

[RobinPicard]

As part of the v1.0 project, we are refactoring the models' and generators' interfaces. A consequence of that change is that the generate tests in file tests/generate/test_generate are inadequate for those new models. We stopped running those tests on refactored models in PR #1413 as they were necessarily failing.

We should write a new set of generate tests fitting the refactored models/generators.