question: public void testGetIssuers ( ) { X509CRLSelector selector = new X509CRLSelector ( ) ; X500Principal iss1 = new X500Principal ( "O=First Org." ) ; X500Principal iss2 = new X500Principal ( "O=Second Org." ) ; X500Principal iss3 = new X500Principal ( "O=Third Org." ) ; assertNull ( "The collection should be null." , selector . getIssuers ( ) ) ; selector . addIssuer ( iss1 ) ; selector . addIssuer ( iss2 ) ; Collection < X500Principal > result = selector . getIssuers ( ) ; try { result . add ( iss3 ) ; fail ( "The returned collection should be unmodifiable." ) ; } catch ( UnsupportedOperationException e ) { } assertTrue ( "The collection should contain the specified DN." , result . contains ( iss2 ) ) ; }
target:  getIssuers() method testing. Tests if the method return null in the case of not specified issuers, if the returned collection corresponds to the specified issuers and this collection is unmodifiable.