public virtual void TestToStringAndMultiAttributeImplementations()
        {
            AttributeSource src     = new AttributeSource();
            ITermAttribute  termAtt = src.AddAttribute <ITermAttribute>();
            ITypeAttribute  typeAtt = src.AddAttribute <ITypeAttribute>();

            termAtt.SetTermBuffer("TestTerm");
            typeAtt.Type = "TestType";
            Assert.AreEqual("(" + typeAtt.ToString() + "," + termAtt.ToString() + ")", src.ToString(), "Attributes should appear in original order");
            System.Collections.Generic.IEnumerator <Attribute> it = src.GetAttributeImplsIterator().GetEnumerator();
            Assert.IsTrue(it.MoveNext(), "Iterator should have 2 attributes left");
            Assert.AreSame(typeAtt, it.Current, "First AttributeImpl from iterator should be typeAtt");
            Assert.IsTrue(it.MoveNext(), "Iterator should have 1 attributes left");
            Assert.AreSame(termAtt, it.Current, "Second AttributeImpl from iterator should be termAtt");
            Assert.IsFalse(it.MoveNext(), "Iterator should have 0 attributes left");

            src = new AttributeSource();
            src.AddAttributeImpl(new Token());
            // this should not add a new attribute as Token implements TermAttribute, too
            termAtt = src.AddAttribute <ITermAttribute>();
            Assert.IsTrue(termAtt is Token, "TermAttribute should be implemented by Token");
            // get the Token attribute and check, that it is the only one
            it = src.GetAttributeImplsIterator().GetEnumerator();
            Assert.IsTrue(it.MoveNext());
            Token tok = (Token)it.Current;

            Assert.IsFalse(it.MoveNext(), "There should be only one attribute implementation instance");

            termAtt.SetTermBuffer("TestTerm");
            Assert.AreEqual("(" + tok.ToString() + ")", src.ToString(), "Token should only printed once");
        }