Down to 3 remote failures, all one chain. The explicit no-events reporting is
working — the diagnostic now states the events file does not exist, instead of
silently printing the generic message. But it then ASSERTED a cause: "the child
was killed before the reporter wrote even one event (process/spawn startup
stall, not a test hang)". That was a guess dressed as a finding, and the fixture
contradicts it: it starts a real test, so test:start should fire in milliseconds
against a 2000ms budget.
Two hypotheses remained and I could not separate them locally, because the local
test runner is hook-blocked here: either the custom reporter never LOADS in the
child, or it loads and no event reaches it before the SIGKILL.
Rather than guess a third time, the artifact now answers it. The reporter
appends a reporter:init line as its first action, before consuming anything, so
the file's contents discriminate: absent means the reporter never loaded;
init-only means it loaded and saw no test events; init plus events means it
works. The diagnostic has a branch for each and, where the cause is genuinely
unresolved, names both possibilities instead of picking one.
Also passes the reporter as a file:// URL via pathToFileURL. Node documents the
--test-reporter value as an import()-style specifier, and a bare absolute path
is not a portable one — notably on Windows. That is a correctness fix whichever
hypothesis holds, and it is a live candidate for the first. FIXED_OVERHEAD is
derived by reducing over the actual argv strings, so the longer URL is accounted
automatically.
Verified by execution, not assumption: composing the reporter against an EMPTY
event stream writes exactly one line, the init marker. That is the whole point
of the marker, so it is pinned by a test rather than left to inspection.
T1 stays red and untouched.
Verification runs on the remote runner.
Refs #4012
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