I have experienced this issue since upgrading from 2017.3 to the latest 2018.1.5. Running a jest test seems to work as expected, but when I switch to debug the same test, it hangs. I have simplified this down to a project with a package.json and a single test file. See screenshots below. I click the green arrow on line 3, then select Debug 'testing', and it hangs in the state pictured below.
Here is my package.json
And here are the configuration settings for the test process