The test AbstractUndertowSubsystemTestCase#testRuntime is flaky because it has Assert.assertEquals("default-alias", new ArrayList<>(host.getAllAliases()).get(1)) where getAllAliases() returns HashSet, so the test checks that "default-alias" is at the second index of the list formed from the set. The modified code checks that "default-alias" is in the HashSet itself. This fixes 10 flaky tests in the subclasses of AbstractUndertowSubsystemTestCase.