XCTests Failing on Physical Device: “Canceling tests due to timeout …”

Question

XCTests are failing with the message: *** Canceling tests due to timeout in Waiting for test process to check in... This just started coming up in the last few days

Answer 1

While I think Werner Altewischer's answer is correct it's always important to look at the earliest error you're seeing, not the latest.

In my case, I was seeing the error that was posted in the question but there were numerous compilation errors before that.

ex.

Testing failed:
    '...' is not a postfix unary operator
    'count' is unavailable: there is no universally good answer, see the documentation comment for discussion
    Cannot convert value of type 'Int' to expected argument type 'IntMax' (aka 'Int64')
    Cannot convert value of type 'Int8' to expected argument type 'IntMax' (aka 'Int64')
    Cannot convert value of type 'Int16' to expected argument type 'IntMax' (aka 'Int64')
    Cannot convert value of type 'Int32' to expected argument type 'IntMax' (aka 'Int64')
    Cannot convert value of type 'UInt' to expected argument type 'UIntMax' (aka 'UInt64')
    Cannot convert value of type 'UInt8' to expected argument type 'UIntMax' (aka 'UInt64')
    Cannot convert value of type 'UInt16' to expected argument type 'UIntMax' (aka 'UInt64')
    Cannot convert value of type 'UInt32' to expected argument type 'UIntMax' (aka 'UInt64')

I eventually realized that I upgraded my environment without updating my targeted Xcode version in in TravisCI.

Changing...

osx_image: xcode8.3

to...

osx_image: xcode9.3

in my .travis.yml fixed this for me.