Xcode UI tests don't automatically launch simulator

Usually when Xcode starts a UI test, it will automatically launch the selected simulator first.

I have a project in which this is broken: if the simulator is not already open, I get this error:

"No devices are booted."


  • This occurs before the test
    setup()
    function is called.
  • If the simulator is already open, everything works as normal.
  • It is local to one specific project and persists if I make a new UI test target in that project
  • The problem does not happen if I make a new project with a new UI test bundle - the simulator launches as per normal.
  • I'm using Xcode 10.2 and have tried resetting simulators as well as reinstalling them.
  • It inteferes with running UI tests in parallel as clones do not launch automatically.


Does anyone know what this could be related to?