How to run headless test for Emulators or Simulators in Appium?

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capabilities.setCapability("isHeadless", true);

Set this capability to true to run emulators or simulators in headless mode. This means that the UI will not be displayed and does not need to be rendered. For iOS, this is only supported in XCode version 9 and later. All running instances of the simulator UI will be terminated when a headless test is started. Value=true/false