Open Radar

 
While executing UIAutomation tests from command line using xcodebuild. The tool allocations enormous amount of pseudo terminals, around one terminal per test case. If the test target has more then 100 tests (in my case 186) the application can reach the maximum number of allowed pseudo terminals (by default 127) and it cannot execute next tests with following error message:

> Assertion Failure: <unknown>:0: UI Testing Failure - Failure attempting to launch <XCUIApplicationImpl: 0x610000030cc0 com.user.test at /Users/user/Library/Developer/Xcode/DerivedData/test-bdhmpkpvtcuzrscnsfkcsgohstze/Build/Products/Debug-iphonesimulator/test.app>: Error Domain=IDEPseudoTerminalDomain Code=1 "(null)"

This issue doesn't occurs if the test were started from Xcode. In case of Xcode the number of allocated pseudo terminals is no higher than 9. It can be checked by executing command:

> sudo lsof /dev/ptmx

As a workaround the maximum number of allowed pseudo terminals can be changed to 999 (this is the maximum number allowed by the system) by using command:

> sudo sysctl -w kern.tty.ptmx_max=999

But if the test target will have more than 1000 tests the issue will come back.

Steps to Reproduce:
1. Using terminal go to folder where the attached project was extracted
2. Execute UI tests using:
xcodebuild -project test.xcodeproj -scheme test -destination "platform=iOS Simulator,name=iPhone 7" build test
3. Tests should fail before `testExample128`

Expected Results:
All test should be executed and finished

Actual Results:
When the maximum number of pseudo terminals is reached the tests are no longer executed and starting failing with "Assertion Failure" error

Version:
masOS Sierra 10.12.1 (16B2555)
Xcode Version 8.1 (8B62)

Notes:
I've attached logs from xcodebuild command and compressed project with tests.