AggregateRealmEvidenceTest has a test that currently tests the case where authentication succeeds with a principal transformer:

https://github.com/wildfly-security/wildfly-elytron/blob/2.x/auth/realm/base/src/test/java/org/wildfly/security/auth/realm/AggregateRealmEvidenceTest.java#L161-L177

Add a similar test case but for the case where authentication fails.