For the BRNSHRK. SendEmailControllerTest
The unit tests in the code are creating simple contacts, accounts, and opportunities. These have very similar (if not the same) names in the test data. Check the settings and rules for Duplicates under Settings->Data Management->Duplicate Management->Duplicate Rules
If you deselect the Alert checkbox for the Operations On Create setting for the Standard Contact Duplicate Rule and all tests should pass. See attached image of the checkbox that caused the issue when selected.