## PR Type
What kind of change does this PR introduce?
<!-- Please uncomment one or more that apply to this PR. -->
- Bugfix
- Build or CI related changes
<!-- - Documentation content changes -->
<!-- - Sample app changes -->
<!-- - Other... Please describe: -->
## What is the current behavior?
<!-- Please describe the current behavior that you are modifying, or link to a relevant issue. -->
Some .NET Core 2.1 unit tests for the base package fail when run locally.
## What is the new behavior?
<!-- Describe how was this issue resolved or changed? -->
All tests run correctly when executed locally.
## PR Checklist
Please check if your PR fulfills the following requirements:
- [X] Tested code with current [supported SDKs](../readme.md#supported)
- [ ] ~~Pull Request has been submitted to the documentation repository [instructions](..\contributing.md#docs). Link: <!-- docs PR link -->~~
- [ ] ~~Sample in sample app has been added / updated (for bug fixes / features)~~
- [ ] ~~Icon has been created (if new sample) following the [Thumbnail Style Guide and templates](https://github.com/windows-toolkit/WindowsCommunityToolkit-design-assets)~~
- [X] Tests for the changes have been added (for bug fixes / features) (if applicable)
- [X] Header has been added to all new source files (run *build/UpdateHeaders.bat*)
- [X] Contains **NO** breaking changes
<!-- If this PR contains a breaking change, please describe the impact and migration path for existing applications below.
Please note that breaking changes are likely to be rejected. -->