public void Unify_str_ref_str()
{
StructureTerm s1 = new StructureTerm("s", 1);
s1.Next = new AbstractTerm();
StructureTerm s2 = new StructureTerm("s", 1);
s2.Next = new ConstantTerm("ali");
Assert.IsTrue(s1.Unify(s2));
Assert.AreEqual(s1[0].Data(), s2[0].Data());
}