Write tests

[SamJakob]

We need to write tests – particularly for the core framework. Here's, what I believe to be, a sensible roadmap for this process:

• Stage 0: choose and set up the initial test framework.
• Stage 1: determine convention for writing tests.
  • Stage 1.0: document convention for writing tests.
  • Stage 1.1: write a few (very) fundamental tests to use as examples.
• Stage 2: write tests for core and simple or critical (to be defined) core modules.
  • Stage 2.0: determine which modules are simple and/or critical - in other words triage Stage 2
  • Stage 2.1: determine the scope and quantity of the tests we'd like to write at this stage (bear in mind, more can be written after the fact)
  • Stage 2.2: write the tests
  • Stage 2.3: compare the tests with our convention and document/resolve any oversights
• Stage 3: implement CI for tests
  • Stage 3.0: consider what, at which points, should be tested (e.g., do we test all modules on every push or pull request or are some tests not relevant)
  • Stage 3.1: commit working CI configuration
  • Stage 3.2: test CI configuration with deliberately invalid commits (perhaps in another branch depending on external framework usage)
• Stage 4: establish and document protocol for writing tests
  • Stage 4.0: consider and document who we will expect to write tests and who, if anyone, it should be restricted to (maintainer only?, approved contributors?, all contributors?), how they should tests be themselves tested and accepted?, what are the expectations and scope of tests in general?