Improve test coverage of the build system

[snowleopard]

The selftest target is currently too limited to be useful. More tests need to be added.

[chitrak7]

Hi @snowleopard, @izgzhen,
Can you please give me an idea of more tests that we can perform.
Also, currently all tests are hardcoded, but I think we can introduce a bit of randomization to make the tests more effective.

[snowleopard]

@chitrak7 We already use QuickCheck. What other randomisation do you have in mind?

[chitrak7]

Eg: The rule testModuleName currently has hardcoded ‘Data.Functor.Identity“. We can instead pick up any Module Randomly and test for that. @snowleopard

[snowleopard]

Right, I see.

I'd say this whole issue is fairly low priority. It's great to have thorough tests to help maintain Hadrian in the long term, but we still have a lot of work before Hadrian becomes the default build system for GHC.

[chitrak7]

@snowleopard Giving it 3-4 days in my proposal. My proposal currently aims at making Hadrian more robust by implementing good test coverage, both from test suite as well as internally.