Try to push any variation testing into testing-concept-fast-tests. Very high level, slow, tests should only test a small handful of variations. This is one of the motivations for testing-concept-view-model-tests
from: parley-thread-fast-tests-for-variation
Fixing an edge case in those views may involve the painstaking process of writing of an end-to-end test to ensure the bug has been squashed. Those kind of tests have quite an impact on the overall runtime of the test suite, so typically you don't want to write too many of them. Especially not for edge cases.
At 8:00 - "It is very very difficult to test fine-grained edge cases and things like that from the outside. It's very difficult to set the world up in this complicated way where this very rare case is triggered."