FleetHealthMonitor.coverage had zero references in the test tree — not the
method, not either output string, not the field it populates. Inverting
`enabled`, swapping "full"/"detection-only", or breaking the argument pairing
at the HealthCoverageSource call site in Fleetd.java all shipped a green
build.
Extract the HealthCoverageSource lambda out of Fleetd.main into a
package-private static factory (healthCoverageSource(ConfigRef)), the same
shape capacitySource/quarantineSource already use for the identical
argument-pairing risk (fleetd #415). #407's "keep the config invalid, assert
on the log line before validateAll() throws" option does not apply here: this
call site is built well after validateAll() and after a real herdr socket
connect, so driving it through a real Fleetd.main would require the socket
I/O this ticket's tests must not do.
Add FleetHealthMonitorCoverageTest (the three-branch method itself) and
FleetdHealthCoverageSourceWiringTest (the call site, via a real
FleetConfig.load + ConfigRef against @TempDir fixtures, including a hot
notifications-reload case). Output strings are unchanged — "detection-only"
is still what a live fleet_list reports today.
Measured: all three mutations killed by the new tests.
Dai Ha