public void EvaluateUndefinedVariable()
 {
     VariableExpression expr = new VariableExpression("Foo");
     Assert.IsNull(expr.Evaluate(this.context));
 }
 public void EvaluateDefinedVariable()
 {
     VariableExpression expr = new VariableExpression("One");
     Assert.AreEqual(1, expr.Evaluate(this.context));
 }