@Test
public void testPollFirstEntry() {

    IncrementalSortMap<Integer, String> map = map5();
    Map.Entry e = map.pollFirstEntry();
    assertEquals(one, e.getKey());
    assertEquals("A", e.getValue());
    e = map.pollFirstEntry();
    assertEquals(two, e.getKey());
    map.put(one, "A");
    e = map.pollFirstEntry();
    assertEquals(one, e.getKey());
    assertEquals("A", e.getValue());
    e = map.pollFirstEntry();
    assertEquals(three, e.getKey());
    map.remove(four);
    e = map.pollFirstEntry();
    assertEquals(five, e.getKey());
    try {
        e.setValue("A");
        shouldThrow();
    }
    catch (UnsupportedOperationException success) {}
    e = map.pollFirstEntry();
    assertNull(e);
}