This failure only occurs when the test machine has at least one printer configured. In CI, the machines have no printers so the test has not failed on Mac in the last 1000 CI runs.
In CI, the testForPrinters test function has the following output:
lpstat: No destinations added.
PASS : tst_QPrinterInfo::testForPrinters()
(a) this test should be changed so that the parts that are inapplicable when no pirnters are on the system will be explicitly skipped.
(b) the CI machines be configured with one or more virtual printers (e.g. print to PDF) so that the test does something meaningful in CI. Even better if the test can control the printer configuration so that tests can be repeated with zero, one, two, and many printers present.