@RunWith(PowerMockRunner.class)
public class ClientTest {
@Test(expected = NullPointerException.class)
public void testAssemblePipelineWhenMainElementIsNull() throws Exception {
SocketWrapper socketMock = mock(SocketWrapper.class);
when(socketMock.getId()).thenReturn("socket");
Whitebox.setInternalState(Client.class, "socket", socketMock);
Element main = null;
Client.assemblePipeline(main);
}