[JENKINS-66861] Add test for CodeMetricSeriesBuilder

[Artmorse]

The issue
You can find all the issue details here.

My updates:
I've created the test for the CodeMetricSeriesBuilder class.

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[codecov]

Codecov Report

Merging #455 (c123de9) into master (831f72a) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #455   +/-   ##
=========================================
  Coverage     71.42%   71.42%           
  Complexity      386      386           
=========================================
  Files            48       48           
  Lines          1169     1169           
  Branches        101      101           
=========================================
  Hits            835      835           
  Misses          293      293           
  Partials         41       41           

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[uhafner]

Thanks for your PR!