Adds a step to preboot a simulator before attempting to run a test on it. Also bumps the simulator to an 'iPhone XS' running iOS 12.1.
Adds a step to preboot a simulator before attempting to run a test on it. Also bumps the simulator to an 'iPhone XS' running iOS 12.1.

Also made changes to ensure each test case is hermetic. A fresh simulator is created before any tests are run and deleted after all tests have completed. The simulator is booted and launched before each test case and is shutdown and wiped after each test case.

PiperOrigin-RevId: 233635794

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