Test suite restructure

In GitLab by @timothy-nunn on Dec 1, 2021, 11:02

Currently, the test suite distinguishes unit, integration, and regression tests. However, the difference between unit and (some) integration tests is becoming less -- some integration tests are currently in the unit tests folder.

Converting to a system where each file contains the unit and integration tests for each module would make more sense and allow fixtures to be contained within that modules test file. Unit and integration tests should be contained within distinct, marked, classes within a file.

Test markers should also be added to separate automatically-generated regression unit tests (RUTs) from human-created tests.

• Add marks for integration and unit tests
• Move all unit and integration tests into the tests folder
• Move existing tests into class-based tests for existing tests
• Document the changes
• Convert tests that still exist outside of the test suite (e.g. test_quench(), brookscoil(nout) and call test_secant_solve()) to pytest tests #749

Start by reviewing the existing tests and the tests folder, especially the out-of-suite examples test_quench(), brookscoil(nout), and call test_secant_solve(). Check how pytest currently distinguishes unit, integration, and regression tests. Done means the tests are reorganized by module with marked unit, integration, and RUT classes, documented, and the named tests converted to pytest tests.