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[bot]]

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

```diff @@ 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](https://app.codecov.io/gh/FollowTheProcess/test/pull/11?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Fleet) | Coverage Δ | | |---|---|---| | [test.go](https://app.codecov.io/gh/FollowTheProcess/test/pull/11?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Tom+Fleet#diff-dGVzdC5nbw==) | `96.20% <57.14%> (-3.80%)` | :arrow_down: |

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[FollowTheProcess]

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