@Test
public void doStopBadConnection() throws Exception {

    Field openRequests = SUT.getClass().getDeclaredField("plcConnection");
    openRequests.setAccessible(true);
    PlcConnection plcConnectionMock = mock(PlcConnection.class);
    doThrow(new RuntimeException("oh noes")).when(plcConnectionMock).close();
    openRequests.set(SUT, plcConnectionMock);
    SUT.doStop();
}