Fix a couple of dotnet-watch test failures (#49558)

Author: tmat

test/dotnet-watch.Tests/HotReload/ApplyDeltaTests.cs

@@ -3,6 +3,8 @@
 
 #nullable disable
 
+using System.Text.RegularExpressions;
+
 namespace Microsoft.DotNet.Watch.UnitTests
 {
     public class ApplyDeltaTests(ITestOutputHelper logger) : DotNetWatchTestBase(logger)
@@ -30,6 +32,8 @@ public static void Print()
                 }
                 """);
 
+            await App.AssertOutputLineStartsWith(MessageDescriptor.ReEvaluationCompleted);
+
             // update existing file:
             UpdateSourceFile(Path.Combine(dependencyDir, "Foo.cs"), """
                 public class Lib
@@ -254,7 +258,7 @@ public async Task DefaultItemExcludes_DefaultItemsEnabled()
             App.Start(testAsset, []);
 
             await App.AssertWaitingForChanges();
-            App.AssertOutputContains(@"dotnet watch ⌚ Exclusion glob: 'AppData/**/*.*;bin\Debug\/**;obj\Debug\/**;bin\/**;obj\/**");
+            App.AssertOutputContains(new Regex(@"dotnet watch ⌚ Exclusion glob: 'AppData/[*][*]/[*][.][*];bin[/\\]+Debug[/\\]+[*][*];obj[/\\]+Debug[/\\]+[*][*];bin[/\\]+[*][*];obj[/\\]+[*][*]"));
             App.Process.ClearOutput();
 
             UpdateSourceFile(appDataFilePath, """

test/dotnet-watch.Tests/Utilities/AssertEx.cs

@@ -6,6 +6,7 @@
 
 using System.Collections;
 using System.Diagnostics;
+using System.Text.RegularExpressions;
 using Xunit.Sdk;
 
 namespace Microsoft.DotNet.Watch.UnitTests
@@ -253,5 +254,26 @@ public static void ContainsSubstring(string expected, IEnumerable<string> items)
 
             Fail(message.ToString());
         }
+
+        public static void ContainsPattern(Regex expected, IEnumerable<string> items)
+        {
+            if (items.Any(item => expected.IsMatch(item)))
+            {
+                return;
+            }
+
+            var message = new StringBuilder();
+            message.AppendLine($"Expected pattern not found in the output:");
+            message.AppendLine(expected.ToString());
+            message.AppendLine();
+            message.AppendLine("Actual output:");
+
+            foreach (var item in items)
+            {
+                message.AppendLine($"'{item}'");
+            }
+
+            Fail(message.ToString());
+        }
     }
 }

test/dotnet-watch.Tests/Watch/Utilities/DotNetWatchTestBase.cs

@@ -30,8 +30,9 @@ public void Log(string message, [CallerFilePath] string? testPath = null, [Calle
 
     public void UpdateSourceFile(string path, string text, [CallerFilePath] string? testPath = null, [CallerLineNumber] int testLine = 0)
     {
+        var existed = File.Exists(path);
         WriteAllText(path, text);
-        Log($"File '{path}' updated", testPath, testLine);
+        Log($"File '{path}' " + (existed ? "updated" : "added"), testPath, testLine);
     }
 
     public void UpdateSourceFile(string path, Func<string, string> contentTransform, [CallerFilePath] string? testPath = null, [CallerLineNumber] int testLine = 0)

test/dotnet-watch.Tests/Watch/Utilities/WatchableApp.cs

@@ -4,6 +4,7 @@
 #nullable disable
 
 using System.Runtime.CompilerServices;
+using System.Text.RegularExpressions;
 
 namespace Microsoft.DotNet.Watch.UnitTests
 {
@@ -39,6 +40,9 @@ public void AssertOutputContains(string message)
         public void AssertOutputDoesNotContain(string message)
             => Assert.DoesNotContain(Process.Output, line => line.Contains(message));
 
+        public void AssertOutputContains(Regex pattern)
+            => AssertEx.ContainsPattern(pattern, Process.Output);
+
         public void AssertOutputContains(MessageDescriptor descriptor, string projectDisplay = null)
             => AssertOutputContains(GetLinePrefix(descriptor, projectDisplay));