
using Xunit;
using Xunit;
using Xunit;
using System;
using System.IO;
using System.Linq;

namespace ConsoleApp {
    public class ProgramTests {
        [Fact(DisplayName = "PrintOddNumbers prints all odd numbers from 1 to 19, each on a new line, and nothing else")]
        public void PrintOddNumbers_PrintsCorrectOddNumbersOnly() 
        {
            // Success: Test passes if the output contains exactly the odd numbers from 1 to 19, each on its own line, and nothing else.
            // Failure: Test fails if any odd number from 1 to 19 is missing, out of order, or if extra/unexpected values are printed, or if output contains non-integer lines.
            var sw = new StringWriter();
            Console.SetOut(sw);

            Program.PrintOddNumbers();

            string output = sw.ToString().Trim();
            string[] lines = output.Split(new[] { '\\n', '\\r' }, StringSplitOptions.RemoveEmptyEntries);
            int[] expected = new[] {1,3,5,7,9,11,13,15,17,19};
            int[] actual;
            try {
                actual = lines.Select(s => int.Parse(s.Trim())).ToArray();
            } catch {
                // Failure: Output contains non-integer lines or not all lines are numbers.
                Assert.True(false, "Output contains non-integer lines or not all lines are numbers");
                return;
            }
            Assert.Equal(expected, actual);
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = true });
        }

        [Fact(DisplayName = "PrintOddNumbers does not print even numbers or numbers outside 1 to 19")]
        public void PrintOddNumbers_DoesNotPrintEvenOrOutOfRange() 
        {
            // Success: Test passes if all printed numbers are odd and between 1 and 19 inclusive.
            // Failure: Test fails if any printed number is even or outside the range 1 to 19.
            var sw = new StringWriter();
            Console.SetOut(sw);

            Program.PrintOddNumbers();

            string output = sw.ToString().Trim();
            string[] lines = output.Split(new[] { '\\n', '\\r' }, StringSplitOptions.RemoveEmptyEntries);
            foreach (string line in lines)
            {
                int val = int.Parse(line.Trim());
                // Failure: Printed value is not odd.
                Assert.True(val % 2 == 1, $"Printed value {val} is not odd");
                // Failure: Printed value is outside the range 1 to 19.
                Assert.InRange(val, 1, 19);
            }
            Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = true });
        }
    }
}

ProgramTests.cs

Deepen your understanding of C# loops with a hands-on, challenge-driven course. Explore for, while, and do-while loops, master nested structures, generate patterns, and tackle real-world problems. Each section alternates between engaging theory and practical coding challenges to ensure you build both conceptual understanding and practical fluency.

Explore the full power of for loops in C#, from basic counting to custom steps and real-world data processing.

Master while and do-while loops for scenarios where the number of iterations isn't known in advance, and learn to control loop execution with conditions.

Delve into advanced looping techniques, including nested loops for pattern generation, loop transformations, efficiency, and avoiding common mistakes.

Challenge: Print Odd Numbers

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Challenge: Print Odd Numbers

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