public void Unify_str_eq_str()
{
StructureTerm s1 = new StructureTerm("s", 2);
s1.Next = new ConstantTerm("ali");
s1.Next.Next = new ConstantTerm("samir");
StructureTerm s2 = new StructureTerm("s", 2);
s2.Next = new ConstantTerm("ali");
s2.Next.Next = new ConstantTerm("samir");
Assert.IsTrue(s1.Unify(s2));
}