returning Nil on empty IntMap as done in corresponding functions for Map

[kushagarr]

Closes #1061

@meooow25

[treeowl]

The link to the issue doesn't work .

[kushagarr]

@treeowl Fixed it.

[treeowl]

Please adjust the property tests accordingly.

[meooow25]

Thanks for the PR. Your change seems fine, but as mentioned above please update/add property tests for affected functions. These will be in containers-tests/intmap-properties.hs.

[treeowl]

@meooow25 , it's obviously not an issue for this PR, but it looks like we only have unit tests for these and many other IntMap functions, and no property tests. That's no good!

[kushagarr]

So, what is it that I should be doing here,
If I take updateMinWithKey as an example, I see only one Assertion called test_updateMinWithKey in containers-tests/tests/intmap-properties.hs.

Should I just update that assertion to have this change also included in that or you want me to add property tests for this as well.
FYI, Although I have read about tests and property tests in Haskell, I haven't really written them in Haskell before, So please bear with me and guide me if I make mistakes.

[meooow25]

I took at look at the tests we have. You could add a new unit test for the empty map case in test_updateMinWithKey, test_updateMaxWithKey, etc. That's good enough for this PR.
Otherwise, if you want to add new property tests for these functions, it would be very helpful. Let us know if you need any help.

...but it looks like we only have unit tests for these and many other IntMap functions, and no property tests. That's no good!

Yes that's not ideal, we should look into having property tests for everything.

[kushagarr]

Not able to come up with property tests yet, apologies.
I need more time may be.

[treeowl]

Not able to come up with property tests yet, apologies. I need more time may be.

Don't worry about that. @meooow25 opened a new issue to deal with that.

[meooow25]

Thanks!