public string ExecuteAddTest(string command)
{
var textReader = Substitute.For<TextReader>();
Console.SetIn(textReader);
var textWriter = Substitute.For<TextWriter>();
Console.SetOut(textWriter);
textReader.ReadLine().Returns(command);
string result = null;
textWriter
.When(w => w.WriteLine(Arg.Any<string>()))
.Do(c => result = c.Arg<string>());
var stringCalculator = new StringCalculator();
stringCalculator.ExecuteAdd(Console.ReadLine());
return result;
}
