Fixing Chap 20 flaky tests

src/Chapter20.Tests/BaseProgramTests.cs

@@ -7,17 +7,17 @@
 
 namespace AddisonWesley.Michaelis.EssentialCSharp.Chapter20.Tests;
 
-abstract public class BaseProgramTests
+public abstract class BaseProgramTests
 {
     [NotNull]
-    static public ProgramWrapper? ProgramWrapper { get; set; }
+    public static ProgramWrapper? ProgramWrapper { get; set; }
 
     protected abstract string DefaultUrl { get; }
 
     [NotNull]
     public TestContext? TestContext { get; set; }
 
-    [TestInitializeAttribute]
+    [TestInitialize]
     public void TestInitialize()
     {
         Assert.IsNotNull(TestContext);
@@ -29,7 +29,7 @@ public void TestInitialize()
     [TestMethod]
     [DataRow("IntelliTect", @"[1-9]\d*")]
     [DataRow("Text Snippet That Does Not Exist On The Page", @"0")]
-    public void Main_FindText_VerifyOccurenceCount(string findText, string countPattern)
+    public void Main_FindText_VerifyOccurrenceCount(string findText, string countPattern)
     {
         string url = DefaultUrl;
         string expected =
@@ -41,10 +41,7 @@ public void Main_FindText_VerifyOccurenceCount(string findText, string countPatt
                 Regex.Escape(url)
                 }'\.\s+";
         string actual = IntelliTect.TestTools.Console.ConsoleAssert.Execute("",
-        () =>
-        {
-            ProgramWrapper.Main(new string[] { findText }).Wait();
-        });
+        () => ProgramWrapper.Main(new string[] { findText }).Wait());
 
         Regex regex = new(expected);
         Assert.IsTrue(regex.Match(actual).Success,
@@ -110,78 +107,22 @@ protected static void AssertAggregateExceptionType(string messagePrefix, Aggrega
         });
     }
 
-    [TestMethod]
-    [ExpectedException(typeof(System.ArgumentNullException))]
-    public async Task Main_GivenNullUri_ThrowException()
-    {
-        try
-        {
-            await ProgramWrapper.Main(new string[] { "irrelevant", null! });
-            Assert.Fail("Expected exception was not thrown.");
-        }
-        catch (AggregateException exception)
-        {
-            if (exception.InnerExceptions.Count != 1)
-            {
-                throw new InvalidOperationException("Unexpected scenario with there being more than one inner exception.");
-            }
-            exception.Handle(innerException =>
-            {
-                // Rethrowing rather than using
-                // if condition on the type
-                ExceptionDispatchInfo.Capture(
-                    innerException!).Throw();
-
-                return true;
-            });
-        }
-    }
+    protected static HttpClient GetMockedHttpClient()
+        => new HttpClient(new MockHttpClientHandler());
+}
 
-    [TestMethod]
-    [DataRow("Bad Uri", "Could not find file *")]
-    [DataRow("https://bad uri", "The filename, directory name, or volume label syntax is incorrect. *", "Could not find a part of the path*", "Could not find a part of the path*")]
-    [DataRow("https://thisisanotherbadurlthatpresumablyldoesnotexist.notexist", "No such host is known.*", "nodename nor servname provided, or not known*", "Name or service not known*")]
-    [ExpectedException(typeof(WebException))]
-    public async Task Main_GivenBadUri_ThrowException(string uri, string defaultMessagePrefix, string? messagePrefixOSX = null, string? messagePrefixLinux = null)
+file class MockHttpClientHandler : HttpMessageHandler
+{
+    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
     {
-        messagePrefixOSX ??= defaultMessagePrefix;
-        messagePrefixLinux ??= defaultMessagePrefix;
-
-        try
-        {
-            await ProgramWrapper.Main(new string[] { "irrelevant", uri });
-            Assert.Fail("Expected exception was not thrown.");
-        }
-        catch (Exception exception)
+        HttpResponseMessage response = new(HttpStatusCode.OK)
         {
-            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
-            {
-                AssertMainException(defaultMessagePrefix, exception);
-            }
-            else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
-            {
-                AssertMainException(messagePrefixOSX, exception);
-            }
-            else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
-            {
-                AssertMainException(messagePrefixLinux, exception);
-            }
-            if (exception is AggregateException aggregateException)
-            {
-                // InnerException expected to be WebException.
-                exception = aggregateException.Flatten();
-                aggregateException.Handle(innerException =>
-                {
-                    // Rethrowing rather than using
-                    // if condition on the type
-                    ExceptionDispatchInfo.Capture(
-                        innerException)
-                        .Throw();
-                    return true;
-                });
-            }
-            // WebException expected
-            else throw;
-        }
+            Content = new StringContent($"""
+            Test Data From {GetType().Namespace}.{nameof(MockHttpClientHandler)}
+            Request Uri: {request.RequestUri},
+            The tests search for the word "IntelliTect" so that is can count the number of times it appears on the page.
+            """)
+        };
+        return Task.FromResult(response);
     }
 }

src/Chapter20.Tests/Listing20.01.Tests.cs

@@ -9,6 +9,7 @@ public class ProgramTests : BaseProgramTests
     [ClassInitialize]
     static public void ClassInitialize(TestContext _)
     {
+        Program.HttpClient = GetMockedHttpClient();
         ProgramWrapper = new ProgramWrapper(
             (args) =>
                 Task.Run(() => Program.Main(args)));

src/Chapter20.Tests/Listing20.02.Tests.cs

@@ -9,6 +9,7 @@ public class ProgramTests : BaseProgramTests
     [ClassInitialize]
     public static void ClassInitialize(TestContext _)
     {
+        Program.HttpClient = GetMockedHttpClient();
         ProgramWrapper = new ProgramWrapper(
             (args) =>
                 Task.Run(() => Program.Main(args)));

src/Chapter20.Tests/Listing20.03.Tests.cs

@@ -9,6 +9,7 @@ public class ProgramTests : BaseProgramTests
     [ClassInitialize]
     public static void ClassInitialize(TestContext _)
     {
+        Program.HttpClient = GetMockedHttpClient();
         ProgramWrapper = new ProgramWrapper(
             (args) =>
                 Task.Run(() => Program.Main(args)));

src/Chapter20/Listing20.01.SynchronousWebRequestHighLatency.cs

@@ -7,6 +7,7 @@ namespace AddisonWesley.Michaelis.EssentialCSharp.Chapter20.Listing20_01;
 
 public static class Program
 {
+    public static HttpClient HttpClient { get; set; } = new();
     public const string DefaultUrl = "https://IntelliTect.com";
 
     public static void Main(string[] args)
@@ -28,9 +29,8 @@ public static void Main(string[] args)
             $"Searching for '{findText}' at URL '{url}'.");
 
         Console.WriteLine("Downloading...");
-        using WebClient webClient = new();
         byte[] downloadData =
-            webClient.DownloadData(url);
+            HttpClient.GetByteArrayAsync(url).Result;
 
         Console.WriteLine("Searching...");
         int textOccurrenceCount = CountOccurrences(

src/Chapter20/Listing20.02.AsynchronousWebRequest.cs

@@ -9,6 +9,7 @@ namespace AddisonWesley.Michaelis.EssentialCSharp.Chapter20.Listing20_02;
 
 public static class Program
 {
+    public static HttpClient HttpClient { get; set; } = new();
     public const string DefaultUrl = "https://IntelliTect.com";
 
     public static void Main(string[] args)
@@ -29,9 +30,8 @@ public static void Main(string[] args)
         Console.WriteLine(
             $"Searching for '{findText}' at URL '{url}'.");
 
-        using WebClient webClient = new();
         Console.Write("Downloading...");
-        Task task = webClient.DownloadDataTaskAsync(url)
+        Task task = HttpClient.GetByteArrayAsync(url)
             .ContinueWith(antecedent =>
             {
                 byte[] downloadData = antecedent.Result;

src/Chapter20/Listing20.03.AsynchronousHighLatencyUsingTaskAsynchronyPattern.cs

@@ -3,11 +3,11 @@ namespace AddisonWesley.Michaelis.EssentialCSharp.Chapter20.Listing20_03;
 #region INCLUDE
 using System;
 using System.IO;
-using System.Net;
 using System.Threading.Tasks;
 
 public static class Program
 {
+    public static HttpClient HttpClient { get; set; } = new();
     public const string DefaultUrl = "https://IntelliTect.com";
 
     public static async Task Main(string[] args)
@@ -28,9 +28,8 @@ public static async Task Main(string[] args)
         Console.WriteLine(
             $"Searching for '{findText}' at URL '{url}'.");
 
-        using WebClient webClient = new();
         Task<byte[]> taskDownload =
-            webClient.DownloadDataTaskAsync(url);
+            HttpClient.GetByteArrayAsync(url);
 
         Console.Write("Downloading...");
         while (!taskDownload.Wait(100))