Update to PHPUnit 8

[C0pyR1ght]

Updated from PHPUnit version 7 -> 8

Codebase changes were needed:

• Updated Composer PHPUnit version to ^8
• Refactored test to work with PHPUnit8
• Added PHPUnit Cache to gitignore

!important: PHPUnit8 requires PHP ^7.2 -> PHP version has to be updated bevor merging.
because of that not all checks are successfull.

//cc @staabm

[staabm]

thx, looks good.

remaining todos in composer.json:

• uplift min php requirement to 7.2
• drop old phpunit versions

adjust travis.yml accordingly

[codecov]

Codecov Report

Merging #142 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #142   +/-   ##
=========================================
  Coverage     93.64%   93.64%           
  Complexity      257      257           
=========================================
  Files            15       15           
  Lines           834      834           
=========================================
  Hits            781      781           
  Misses           53       53

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[staabm]

interessting.. the php 7.4 build uses phpunit 6.x.. it should be phpunit 8.x though

-> ah prefer-lowest build :-)

[C0pyR1ght]

todos done, CI checks are successfull.
ready for merging.

@staabm

[staabm]

looks really good, thx.

well done!