zkg install does not run tests for dependencies

[bbannier]

When installing a package zkg by default runs the unit tests of the package, and not running unit tests requires explicit opt-out via --skiptests. We use this behavior e.g., to run tests against analyzers in CI.

If a package pulls in others via depends however the tests of the dependencies are not run. I am not sure whether this is by (undocumented) design, or by accident, but it definitely was gotcha moment for me since it deviated from my expectations ("zkg surely runs tests for every install"). The current zkg install docs are at least ambiguous here in how they talk of unit tests for packages,

  --skiptests          Skip running unit tests for packages before installation. (default: False)

This e.g., tripped me up with https://github.com/zeek/spicy-analyzers which is a metapackage without its own tests which just aggregates other packages. There currently seems no way to run the tests of the dependencies directly zkg: zkg test bails since the package has no tests, zkg install does not allow running tests of dependencies. Instead one would have to explicitly query the dependencies and test them manually, e.g., this kind of gymnastics

$ zkg info --json spicy-analyzers |
        jq -r 'to_entries | .[] | select(.key|contains("spicy-analyzers")) | .value.metadata[].depends | to_entries | .[].key' | 
        xargs -n1 zkg test