test: bring the test assembly to 100% line coverage

tests/Wolfgang.TryPattern.Tests.Unit/DocExampleCompilationTests.cs

@@ -45,14 +45,9 @@ public class DocExampleCompilationTests
 
     public static IEnumerable<object[]> AllDocExamples()
     {
+        // A missing XML doc file (GenerateDocumentationFile off) throws
+        // FileNotFoundException from Load, naming the path.
         string xmlPath = Path.ChangeExtension(LibraryAssembly.Location, ".xml");
-        if (!File.Exists(xmlPath))
-        {
-            // Missing XML doc: repo-level GenerateDocumentationFile is required.
-            // Test harness will surface this as "no examples found".
-            yield break;
-        }
-
         XDocument doc = XDocument.Load(xmlPath);
         int index = 0;
         foreach (XElement member in doc.Descendants("member"))
@@ -148,14 +143,19 @@ private static void Process(int item) { }
             .Where(d => d.Severity == DiagnosticSeverity.Error)
             .ToList();
 
-        if (errors.Count > 0)
-        {
-            Assert.Fail(CompileFailureMessage.Format(
+        // Unconditional so the message builder runs on a pass too (a
+        // failure-only branch can never reach the 100% test-coverage gate).
+        Assert.True
+        (
+            errors.Count == 0,
+            CompileFailureMessage.Format
+            (
                 $"XML doc example on `{memberName}` (example index {index}) failed to compile.",
                 errors,
                 snippet,
-                "Fix the snippet in the source XML doc, or if it needs an additional using, add it inline in the `<code>` block."));
-        }
+                "Fix the snippet in the source XML doc, or if it needs an additional using, add it inline in the `<code>` block."
+            )
+        );
     }
 }
 

tests/Wolfgang.TryPattern.Tests.Unit/PropertyTests.cs

@@ -45,18 +45,13 @@ public Property Try_Run_of_non_throwing_action_always_succeeds()
     public Property Try_Run_of_throwing_action_carries_message_round_trip(NonEmptyString message)
     {
         if (message is null) throw new ArgumentNullException(nameof(message));
-        // NonEmptyString excludes only the empty string; Result.Failure
-        // additionally rejects whitespace-only strings and there's a
-        // latent bug (#273) that lets a whitespace exception message
-        // escape from Try.Run. Skip that case so the fast-path
-        // property is well-formed vs the current API.
+        // NonEmptyString can still be whitespace-only. Since #273 Try.Run
+        // reports such a message as the exception's type name, because
+        // Result.Failure rejects whitespace.
         string msg = message.Get;
-        if (string.IsNullOrWhiteSpace(msg))
-        {
-            return true.ToProperty();
-        }
+        string expected = string.IsNullOrWhiteSpace(msg) ? nameof(InvalidOperationException) : msg;
         Result r = Try.Run(() => throw new InvalidOperationException(msg));
-        return (r.Failed && string.Equals(r.ErrorMessage, msg, StringComparison.Ordinal)).ToProperty();
+        return (r.Failed && string.Equals(r.ErrorMessage, expected, StringComparison.Ordinal)).ToProperty();
     }
 
 

tests/Wolfgang.TryPattern.Tests.Unit/ReadmeExampleCompilationTests.cs

@@ -67,12 +67,9 @@ public class ReadmeExampleCompilationTests
 
     public static IEnumerable<object[]> AllReadmeFences()
     {
+        // LocateReadme returns a non-existent path when nothing is found,
+        // so ReadAllText throws FileNotFoundException naming it.
         string readmePath = LocateReadme();
-        if (!File.Exists(readmePath))
-        {
-            yield break;
-        }
-
         string content = File.ReadAllText(readmePath);
         // Matches ```csharp\n...content...\n``` — the ``` opener/closer
         // must be at the start of its own line. `Singleline` lets `.`
@@ -160,14 +157,19 @@ private static void Process(int item) { }
             .Where(d => d.Severity == DiagnosticSeverity.Error)
             .ToList();
 
-        if (errors.Count > 0)
-        {
-            Assert.Fail(CompileFailureMessage.Format(
+        // Unconditional so the message builder runs on a pass too (a
+        // failure-only branch can never reach the 100% test-coverage gate).
+        Assert.True
+        (
+            errors.Count == 0,
+            CompileFailureMessage.Format
+            (
                 $"README fence #{index} failed to compile.",
                 errors,
                 snippet,
-                "Fix the fence in README.md, or if it uses framework types the test project doesn't reference (SqlConnection, ASP.NET Core, EF dbContext), add a marker string to ReadmeExampleCompilationTests.SkipMarkers."));
-        }
+                "Fix the fence in README.md, or if it uses framework types the test project doesn't reference (SqlConnection, ASP.NET Core, EF dbContext), add a marker string to ReadmeExampleCompilationTests.SkipMarkers."
+            )
+        );
     }
 
 
@@ -177,16 +179,11 @@ private static string LocateReadme()
         // README.md. On CI the test runs from bin/Release/net10.0/,
         // so the repo root is a few levels up.
         string? dir = AppContext.BaseDirectory;
-        for (int depth = 0; depth < 10 && dir is not null; depth++)
+        while (dir is not null && !File.Exists(Path.Combine(dir, "README.md")))
         {
-            string candidate = Path.Combine(dir, "README.md");
-            if (File.Exists(candidate))
-            {
-                return candidate;
-            }
             dir = Path.GetDirectoryName(dir);
         }
-        return "README.md";  // last-ditch, caller checks Exists
+        return Path.Combine(dir ?? AppContext.BaseDirectory, "README.md");
     }
 }
 

tests/Wolfgang.TryPattern.Tests.Unit/RunAsyncFuncTests.cs

@@ -339,11 +339,15 @@ public async Task RunAsync_Func_CancellationToken_int_when_cancellation_is_reque
         using var cts = new CancellationTokenSource();
         var functionStarted = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
 
-        async Task<int> Function()
+        // Never completes on its own: the only way out is the token, so
+        // there is no unreachable `return` after an infinite delay.
+        var pending = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
+        using var registration = cts.Token.Register(() => pending.TrySetCanceled(cts.Token));
+
+        Task<int> Function()
         {
             functionStarted.TrySetResult(true);
-            await Task.Delay(Timeout.Infinite, cts.Token);
-            return 42;
+            return pending.Task;
         }
 
         var task = Try.RunAsync((Func<Task<int>>)Function, cts.Token);
@@ -374,6 +378,11 @@ Task<int> Function()
         // Act & Assert
         await Assert.ThrowsAsync<OperationCanceledException>(() => Try.RunAsync((Func<Task<int>>)Function, cts.Token));
         Assert.False(wasInvoked, "function should not be invoked when the token is already canceled");
+
+        // Positive control: the probe does flip when the function runs, so
+        // the assertion above is not vacuous.
+        await Function();
+        Assert.True(wasInvoked);
     }
 
 
@@ -395,5 +404,10 @@ public async Task RunAsync_Func_nullable_when_token_is_already_canceled_throws_O
         // Act & Assert
         await Assert.ThrowsAsync<OperationCanceledException>(() => Try.RunAsync((Func<Task<int?>>)Function, cts.Token));
         Assert.False(wasInvoked, "function should not be invoked when the token is already canceled");
+
+        // Positive control: the probe does flip when the function runs, so
+        // the assertion above is not vacuous.
+        await Function();
+        Assert.True(wasInvoked);
     }
 }