Standarize testing patterns

[wojtek0806]

As per comment in PR #1040, I would like us to discuss the established patterns for testing in this library, these will include:

• What we test in unit and functional tests, mainly the scope of those tests.
• The format of test fixtures, e.g out with teardown() in with yield
• Factory classes to reduce the amount of repetitive code.
• When not to test certain elements, e.g due to specifics of BIGIP operation, or limitations, whether its feasible to work around those.
• Adherence to code coverage, e.g. no 100% code coverage (whenever possible) means no PR approval

@caphrim007 @jasonrahm @zancas @pjbreaux

[wojtek0806]

closing as there seems to be no interest in this

[caphrim007]

re-opening. this still needs to be fixed. there is no lack of interest

[wojtek0806]

since we are on this topic, adding code coverage tests at some point should happen. We can push whatever we need now but to test coverage with PR and remain consistent, we would have to go through each lib and address this in separate PRs @caphrim007