Xcode 10 XCTest error: "Underlying error: Test session exited(1) without checking in.)"

Question

I'm working on getting an iOS project ready for Xcode 10 and Swift 4.2. So far I can build and use the app. UI Tests also run properly.

However, I'm having trouble running Unit Tests, getting the following error:

MyApp.app (37040) encountered an error (Early unexpected exit, operation never finished bootstrapping - no restart will be attempted. Underlying error: Test session exited(1) without checking in.)

I've seen the "Early unexpected exit" error before, specially when working on CI and iOS Simulator fails to launch. But I believe this is the first time I see the "Test session exited(1) without checking in" part.

I would like to add that we are getting this error only when running tests from the Xcode IDE. All tests pass properly when run from the command line with xcodebuild.

Answer 1

Deleting and adding Unit tests target worked for me. Don't forget to check new target in "Target Membership" for tests files.