Xcode 9 - test object X detected an error (cannot connect to the test manager)

Question

I try to run some of my unit tests, but it kept giving me an error:

Showing Recent Issues Test target X encountered an error (Unable to connect to test manager on d7306c4130298fbc17bc0985ec02f808dcdc1374 If you believe this error represents a bug, please attach the log file at /var/folders/2h/0y4yjs6s7l307mbr6pk1xdl00000gn/T/com.apple.dt.XCTest/IDETestRunSession-CF80FA05-C8ED-4FCE-A04B-4A8070F21059/X-E8F39B10-0CDC-43D5-9BED-CD2D0F6081DA/Session-X-2018-01-08_161733-D3YlRc.log) 

I tried looking for this type of error, but to no avail. Does anyone have any ideas?

Answer 1

I solved this problem by performing a hard restart of my device. For my iPhone 8, I followed these instructions from macrumors.com: Hard reset iPhone 8

Alternatively, if you are a libimobiledevice user, you can use /usr/local/bin/idevicediagnostics restart from your mac terminal.

Hope this helps

Answer 2

I have the same problem too. At the moment, I resorted to testing on Simulator, which still works. It seems like it started after I upgraded to Xcode 9.2.

Answer 3

I restarted my iPhone 6 (iOS 11.2.6) in the usual way to solve the same problem.