@Test (expected = IllegalStateException.class)
    public void assertSharingAnnotationInstance() {
        SpanNode testNode = new Span(0, 2);
        tree.annotate(testNode, an1);
    }
@author <a href="mailto:mpraveen@yahoo-inc.com">Praveen Mohan</a>

This test covers all possible scenarios in AlternateSpanList.
If you really want to debug, just turn on the debug flag to true.
document/src/test/java/com/yahoo/document/annotation/AlternateSpanListAdvTestCase.java