public void CreateEmptyTuple()
{
var expr = new TupleExpression(new IExpression[] { });
Assert.IsFalse(expr.HasVariable());
var result = expr.Evaluate(null);
Assert.IsNotNull(result);
Assert.IsInstanceOfType(result, typeof(Tuple));
var tuple = (Tuple)result;
Assert.AreEqual(0, tuple.Arity);
}