Add a function to easily retrieve the path to the testdata directory

[FollowTheProcess]

Description

Motivation and Context

Closes #

How Has This Been Tested?

Checklist

• I have updated the documentation if needed.
• I have updated the tests if needed.

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (709d413) 100.00% compared to head (aabc583) 96.20%.

Additional details and impacted files

@@             Coverage Diff             @@
##              main      #11      +/-   ##
===========================================
- Coverage   100.00%   96.20%   -3.80%     
===========================================
  Files            1        1              
  Lines           72       79       +7     
===========================================
+ Hits            72       76       +4     
- Misses           0        2       +2     
- Partials         0        1       +1     

Files	Coverage Δ
test.go	96.20% <57.14%> (-3.80%)	⬇️

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[FollowTheProcess]

Sadly coverage has gone down but the only uncovered section is os.Getwd() which we can't make fail