code: @Test public void testInvalidConstructor(){
    ReadableByteChannel channel=new ReadableByteChannelMock(new String[]{"stuff;","more stuff"},"US-ASCII");
    HttpParams params=new BasicHttpParams();
    SessionInputBuffer inbuf=new SessionInputBufferImpl(1024,256,params);
    try {
      new IdentityDecoder(null,null,null);
      Assert.fail("IllegalArgumentException should have been thrown");
    }
   catch (  IllegalArgumentException ex) {
    }
    try {
      new IdentityDecoder(channel,null,null);
      Assert.fail("IllegalArgumentException should have been thrown");
    }
   catch (  IllegalArgumentException ex) {
    }
    try {
      new IdentityDecoder(channel,inbuf,null);
      Assert.fail("IllegalArgumentException should have been thrown");
    }
   catch (  IllegalArgumentException ex) {
    }
  }
  