Use code coverage as a "utility value" for PropEr (quickcheck) to maximize

[fenollp]

I just ran some properties hard to reach code branches and demonstrated that targeted PBT when informed about coverage gives better results than when not informed!
Have a look at this simple sample code. Here is how it ran

I'm opening this issue to discuss how coverage-targeted PBT can be added to PropEr.

• should a macro such as ?MAXIMIZE_COVERAGE() be introduced to targeted ?FORALLs?
• should cover usage be explicit or should tools such as rebar3 do their own handling of modules to recompile?
• on a scale from YES to OMG, how amazing is this? (I'm excited)

Targeted PBT is an amazing idea. @TheGeorge (Andreas Löscher) & @kostis you guys have done a great job! Please continue!
Do you intend to add other search strategies such as using genetic algorithms or linear regression (as mentioned in your ISSTA’17 paper)?

Note: not a duplicate of #113

[fenollp]

How BTW the tutorial page on TPBT is not using the latest API. I had to look through the ?EXISTS tests module to understand the API. Please tell me if my property can be better stated :)

I'd like to be explicit in the strategies used in my property, how can I do that?
I would like to try on the hill_climbing strategy too.