Error Message

This message may appear when trying to build an iOS app. Sometimes the simulators are not ready before the build step. In this case, you can pre-start the simulators:

# ...
steps:
  - run:
      name: pre-start simulator
      command: xcrun instruments -w "iPhone 11 Pro (13.3) [" || true

Note: the [ character is necessary to uniquely identify the iPhone 7 simulator, as the phone + watch simulator is also present in the build image:

• iPhone 11 Pro (13.3) [<uuid>] for the iPhone simulator.
• iPhone 11 Pro (13.3) + Apple Watch Series 5 - 40mm (6.1.1) [<uuid>] for the phone + watch pair.

Additional Considerations

You can also add the following run step to check for available simulators:

- run: xcrun simctl list &>/dev/null

Additional Resources

• Optimization Best Practices
• Using MacOS