public void Operator_WhenInputIs2118_ShouldBePlus()
{
Captcha captcha = new Captcha(2, 1, 1, 8);
String oper = captcha.Operator();
Assert.AreEqual("+", oper);
}
public void Operator_WhenInputIs2138_ShouldBeMultiply()
{
Captcha captcha = new Captcha(2, 1, 3, 8);
String oper = captcha.Operator();
Assert.AreEqual("-", oper);
}