Nondecisive tests can be useful
The Turing Test isn't a definitive litmus test for intelligence, and failing isn't decisive, but this doesn't make it a bad test. Many good tests are nondecisive but useful.
Copeland cites fingerprints as an example of a test that is nondecisive (as fingerprint tests can be foiled by gloves) but still useful nonetheless.
Jack Copeland, 1993.