public void Unify_ref_con()
{
AbstractTerm term = new AbstractTerm();
ConstantTerm con = new ConstantTerm();
Assert.IsTrue(term.Unify(con));
Assert.AreEqual(term.Data(), con.Data());
Assert.AreSame(term.Reference(), con.Reference());
Assert.IsTrue(term.IsConstant);
Assert.IsFalse(term.IsReference);
}