@Test
    public void testMissingUsernamePasswordAuthenticator() {
        val formClient = new DirectFormClient(null);
        TestsHelper.expectException(() -> formClient.getCredentials(new CallContext(MockWebContext.create(), new MockSessionStore())),
            TechnicalException.class, "authenticator cannot be null");
    }
This class tests the {@link DirectFormClient} class.

@author Jerome Leleu
@since 1.8.6
pac4j-http/src/test/java/org/pac4j/http/client/direct/DirectFormClientTests.java