Unity Editor freezes after running a test in Play mode

Steps to Reproduce:

1. Open attached project.
2. Open Test Runner window. (Window >> General >> Test Runner).
3. Go to PlayMode.
4. Click on 'Create PlayMode Test Assembly Folder' button.
5. Click on 'Create Test Script in current folder' button.
6. Run single test or all tests by clicking on 'Run All' button.

Note: Refer attached video.

Actual result:
Unity editor freezes and never exits after running a test in Test Runner.

Expected Result:
The test should run successfully without freezing the editor.

Environment:
Windows 10, Windows 7, Mac 10.13, Mac 10.12

Occurring with:
2018.3.0a8, 2018.3.0a6, 2018.3.0a4

Working fine with:
2018.3.0a3, 2018.2.0f2