@Test
public void testClearProgress() throws Exception {

    Map<String, Object> contextMap = Maps.newHashMap();
    ProgressControl control = new ProgressControl(UPLOAD_ID, 100);
    control.setContextMap(contextMap);
    assertNull(contextMap.get(ATTRIBUTE_NAME));
    control.advance(50);
    assertNotNull(contextMap.get(ATTRIBUTE_NAME));
    control.clearProgress();
    assertNull(contextMap.get(ATTRIBUTE_NAME));
}