This makes the 5.15 and 6.x branches more comparable, as in 6.0 the
preferred way is to use the non-static methods (which avoids an
expensive lookup in 6.x).
As a drive-by, Avoid memory leaks if the test fails.
Pick-to: 6.0 6.1 5.15
Change-Id: I95b133342a4ea19dd23c235a408f38089706412b
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>