Change mutators and use set in config for Gradle 5

[sinaneski]

• Add how to change mutators in pitest gradle.build config
• Use set() method to prevent Gradle warnings like 'cannot assing a value to final field'

[szpak]

@sinaneski Thanks for your report. I've just started working on deprecation warnings (#155), but I hasn't encountered those mentioned by you.

Could you paste sample configuration which triggers the aforementioned warnings (and Gradle version that you use)?

[sinaneski]

Hi,

I'm using Gradle 5.6.3 version.

However, I got this warning from IntelliJ inspection.

Cannot assign a value to final field 'outputFormats' 
 Inspection info: Reports invalid assignments to final variables, parameters and fields and not initialized final fields.

The inspection is OK after changing the assignment using the set operation.

[szpak]

It is a limitation of Idea. Gradle do some magic to keep the old syntax with = work with final fields (using the setters internally). I will add a point in README that the alternative syntax exists. Unfortunately it is more verbose and less readable :-(.