These tests cover HTTP-specified behaviours for caches, primarily from RFC7234, but as seen through the lens of Fetch.
A few notes:
By its nature, caching is optional; some tests expecting a response to be cached might fail because the client chose not to cache it, or chose to race the cache with a network request.
Likewise, some tests might fail because there is a separate document-level cache that's ill-defined; see this issue.
Partial content tests (a.k.a. Range requests) are not specified in Fetch; tests are included here for interest only.
Some browser caches will behave differently when reloading / shift-reloading, despite the cache mode staying the same.
At the moment, Edge doesn't appear to using HTTP caching in conjunction with Fetch at all.