Testing `dnf4 bootc`

[evan-goode]

The DNF 4 bootc plugin needs integration tests, and ci-dnf-stack is not equipped to test things meant for OSTree systems. Some unanswered questions are:

• Where should test source code live? IMO, as much as possible should be in this upstream repository.
• What testing framework should we use?
• Where should the tests run (GHA, CoreOS Jenkins, Testing Farm)?
• Should we write the tests from scratch, or base them on existing rpm-ostree and/or bootc tests?
• Will any of the answers to the above need to change as development of the bootc plugin progresses?

[evan-goode]

cc @cgwalters

[cgwalters]

Where should the tests run (GHA, CoreOS Jenkins, Testing Farm)?

I think Testing Farm is likely the most practical. (Which also points to the "testing framework" issue, we've tried to make tmt work)

Should we write the tests from scratch, or base them on existing rpm-ostree and/or bootc tests?

There may be some bits that could be copied, but I'm not sure how much. Probably the most interesting thing here is that at least on the bootc side we build a container with the updated bootc and test that.

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In the more medium term I think we may try to reprioritize "run bootc/ostree in a container" which would dramatically simplify this story.