using System;

using Xunit;

public class UnitTests

{

    [Fact]

    public void ConvertToIntNegative()

    {

        // ARRANGE

        int expected = -1;

        int actual;

        // ACT

        string userInput = "-1"; // Simulating user input of "-1"

        bool parseResult = int.TryParse(userInput, out actual);

​

        // ASSERT

        Assert.True(parseResult);

        Assert.Equal(expected, actual);

    }

     [Fact]

    public void ConvertToIntString()

    {

        // ARRANGE

        string userInput = "hello"; // Simulating user input of "hello"

        // ACT

        int actual;

        bool parseResult = int.TryParse(userInput, out actual);

​

        // ASSERT

        Assert.False(parseResult); // Parsing should fail

    }

    [Fact]

    public void ValidateInputValid()

    {

         // ARRANGE

         int score = 50;

​

         // ACT

         bool isValid = Program.ValidateInput(score);

​

         // ASSERT

         Assert.True(isValid);

    }

    [Fact]

    public void ValidateInputInvalid()

    {

        // ARRANGE

        int score = -5;

​

         // ACT

        bool isValid = Program.ValidateInput(score);

​

        // ASSERT

        Assert.False(isValid);

}

}

​

​

public class Program

{

    public static void Main()

    {

        int totalScores = 0;

        int numScores = 0;

        bool stop = false;

​

        while (!stop)

        {

            string userInput = GetUserInput();

​

            if (userInput.ToLower() == "stop")

            {

                stop = true;

            }

            else if (int.TryParse(userInput, out int intScore) && ValidateInput(intScore))

            {

                totalScores += intScore;

                numScores++;

            }

            else

            {

                Console.WriteLine("Input incorrect, try again.");

            }

        }

​

        if (numScores > 0)

        {

            double average = CalculateAverage(totalScores, numScores);

            Console.WriteLine($"Average score: {average:F2}");

        }

​

    }

​

    public static string GetUserInput()

    {

        Console.Write("Enter a score or 'stop' to end: ");

        return Console.ReadLine();

    }

​

    public static bool ValidateInput(int score)

    {

        return score >= 0;

    }

​

    public static double CalculateAverage(int total, int count)

    {

        if (count == 0)

            return 0;

​

        return (double)total / count;

    }

}

​