public void ClearTest()
{
calculator.AddNumber(3);
calculator.AddNumber(9);
calculator.AddOperation(Operation.Addition);
Assert.DoesNotThrow(() => calculator.Calculate());
calculator.Clear();
calculator.AddNumber(5);
calculator.AddNumber(10);
Assert.Throws <MissingOperationException>(() => calculator.Calculate());
calculator.Clear();
calculator.AddNumber(3);
calculator.AddOperation(Operation.Addition);
Assert.Throws <MissingOperandException>(() => calculator.Calculate());
}
