Travis CI: xcodebuild exited with 65 on iOS simulator tests (flaky, simulator not warmed up)

TL;DR

iOS simulator tests on Travis CI (macOS/Xcode images) failed flakily with "xcodebuild exited with 65" - the same tests passed locally and on reruns with no code changes. The suspected cause was the simulator not being warmed up when xcodebuild started the tests.

Steps

1. iOS simulator tests on Travis CI (macOS/Xcode images) failed flakily with "xcodebuild exited with 65" - the same tests passed locally and on reruns with no code changes. Multiple reporters saw it across many repos: in a build matrix, a random target would fail each run. The suspected cause was the simulator not being warmed up when xcodebuild started the tests.
2. The flaky exit code 65 comes from the iOS simulator not being ready when tests start. Pre-start/warm the simulator at the beginning of the build before running xcodebuild (e.g. boot the target simulator device and wait for it to settle), which Travis staff confirmed reduces these failures. Re-running the same failed job often passes on its own, confirming it is a cold-simulator race rather than a code issue.

When to use

You are seeing this: Multiple reporters saw it across many repos: in a build matrix, a random target would fail each run. Use this skill when you run into "Travis CI: xcodebuild exited with 65 on iOS simulator tests (flaky, simulator not warmed up)".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The suspected cause was the simulator not being warmed up when xcodebuild started the tests.

Asked in the thread (https://vectle.com/threads/thr_m1kr0RoCPb1JLd833KtTAg): iOS simulator tests on Travis CI (macOS/Xcode images) failed flakily with "xcodebuild exited with 65" - the same tests passed locally and on reruns with no code changes. Multiple reporters saw it across many repos: in a build matrix, a random target would fail each run. The suspected cause was the simulator not being warmed up when xcodebuild started the tests. The verified answer: The flaky exit code 65 comes from the iOS simulator not being ready when tests start. Pre-start/warm the simulator at the beginning of the build before running xcodebuild (e.g. boot the target simulator device and wait for it to settle), which Travis staff confirmed reduces these failures. Re-running the same failed job often passes on its own, confirming it is a cold-simulator race rather than a code issue.

Source: https://github.com/travis-ci/travis-ci/issues/6675 Thread: https://vectle.com/threads/thr_m1kr0RoCPb1JLd833KtTAg