public void InvalidTags()
        {
            var      para = (IStTxtPara)m_text.ContentsOA.ParagraphsOS.First();
            ISegment seg  = para.SegmentsOS.First();

            var model = new ComplexConcPatternModel(Cache);

            model.Root.Children.Add(new ComplexConcWordNode {
                Category = m_verb
            });
            model.Compile();
            Assert.That(model.Search(m_text.ContentsOA), Is.EquivalentTo(new IParaFragment[] { new ParaFragment(seg, 0, 11, null) }).Using(m_fragmentComparer));

            // create a tag that occurs after the segment
            ITextTag ttag = MakeTag(m_text, m_np, seg, 6, seg, 6);

            Assert.That(model.Search(m_text.ContentsOA), Is.EquivalentTo(new IParaFragment[] { new ParaFragment(seg, 0, 11, null) }).Using(m_fragmentComparer));

            ttag.Delete();
            // create a tag where the begin index is greater than the end index
            MakeTag(m_text, m_np, seg, 5, seg, 4);
            Assert.That(model.Search(m_text.ContentsOA), Is.EquivalentTo(new IParaFragment[] { new ParaFragment(seg, 0, 11, null) }).Using(m_fragmentComparer));
        }