Dear Sumantro,
Did you talk to DNF QE team? I suggest you coordinate your work with Karel Srot from DNF
QE team. There is a tool to test DNF and I know Karel already has a good set of tests
which covers Modular side of DNF [1], just missing some user stories.
There is also a regular DNF Devs and DNF QE mtg, where we discuss all around DNF QA and
particularly Modular DNF, and if you want to contribute you are welcome to join, just
please ping Karel all about it.
Also please mind we have a modular DNF BZ tracker [2].
[1]
https://github.com/rpm-software-management/ci-dnf-stack/tree/modularity
[2]
https://bugzilla.redhat.com/show_bug.cgi?id=1478068