@Test
    public void testWWWAuthenticateNegotiateHeaderIsSetToTriggerSPNEGOWhenNoCredentialsAreFound() {
        final WebContext context = MockWebContext.create();
        val client = new DirectKerberosClient(new KerberosAuthenticator(krbValidator));
        val credentials = client.getCredentials(new CallContext(context, new MockSessionStore()));
        assertFalse(credentials.isPresent());
        assertEquals("Negotiate", context.getResponseHeader(HttpConstants.AUTHENTICATE_HEADER).get());
    }
Tests the Kerberos client with mocked Kerberos authenticator/validator (i.e. no real tickets used)

@author Garry Boyce
@author Vidmantas Zemleris
@since 2.1.0
pac4j-kerberos/src/test/java/org/pac4j/kerberos/client/direct/KerberosClientTests.java