public void AdditionString_StringAndString_ReturnsConcatenatedString(string input1, string input2, string expected)
{
StringLiteralExpression strLit1 = new StringLiteralExpression(input1.ToString(), 1, 1);
StringLiteralExpression strLit2 = new StringLiteralExpression(input2.ToString(), 2, 2);
AdditionExpression addExpr = new AdditionExpression(strLit1, strLit2, 1, 1);
IInterpreterString parent = Substitute.For <IInterpreterString>();
parent.DispatchString(strLit1, Arg.Any <List <object> >()).Returns(input1);
parent.DispatchString(strLit2, Arg.Any <List <object> >()).Returns(input2);
StringHelper stringHelper = SetUpHelper(parent);
string res = stringHelper.AdditionString(addExpr, new List <object>());
Assert.AreEqual(expected, res);
}