[PhingTask] Added reference inheritance test

[siad007]

Related to #1241

[codecov]

Codecov Report

Merging #1270 into master will increase coverage by 0.06%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1270      +/-   ##
============================================
+ Coverage     51.52%   51.58%   +0.06%     
  Complexity     9320     9320              
============================================
  Files           480      480              
  Lines         22860    22860              
============================================
+ Hits          11778    11792      +14     
+ Misses        11082    11068      -14

Impacted Files	Coverage Δ	Complexity Δ
classes/phing/tasks/system/PhingTask.php	74.5% <0%> (+6.86%)	73% <0%> (ø)	⬇️

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