@Test
public void testPutNull() {

    for (IntervalMap set : getAllInstances()) {
        boolean thrown = false;
        try {
            set.put(new Interval(1.0, 2.0), null);
        } catch (NullPointerException e) {
            thrown = true;
        }
        if (!thrown) {
            Assert.fail("Didn't throw an exception for " + set.getClass());
        }
    }
}