Guard TestOutputHelper.WriteLine calls against lifetime exceptions

Directory.Packages.props

@@ -4,7 +4,6 @@
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
     <PackageVersion Include="Microsoft.NETCore.Platforms" Version="5.0.2" />
     <PackageVersion Include="Microsoft.NETCore.Targets" Version="5.0" />
-    <PackageVersion Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.3" />
     <PackageVersion Include="Microsoft.TestPlatform.ObjectModel" Version="16.11" />
     <PackageVersion Include="MSTest.TestAdapter" Version="3.7.0" />
     <PackageVersion Include="MSTest.TestFramework" Version="3.7.0" />

src/FsCheck.Xunit/CheckExtensions.fs

@@ -6,29 +6,39 @@ open FsCheck
 open Xunit.Abstractions
 
 module private Helper =
+    // Helper to safely write to output, handling case where test may have completed
+    let private safeWriteLine (testOutputHelper: ITestOutputHelper) (message: string) =
+        try
+            testOutputHelper.WriteLine(message)
+        with
+        | :? InvalidOperationException -> 
+            // Test has completed, TestOutputHelper is no longer active
+            // Silently ignore as this is expected when runners outlive test lifetime
+            ()
+
     let private runner (testOutputHelper: ITestOutputHelper) =
         { new IRunner with
             member __.OnStartFixture t =
-                Runner.onStartFixtureToString t |> testOutputHelper.WriteLine
+                Runner.onStartFixtureToString t |> safeWriteLine testOutputHelper
             member __.OnArguments (ntest,args, every) =
-                every ntest args |> testOutputHelper.WriteLine
+                every ntest args |> safeWriteLine testOutputHelper
             member __.OnShrink(args, everyShrink) =
-                everyShrink args |> testOutputHelper.WriteLine
+                everyShrink args |> safeWriteLine testOutputHelper
             member __.OnFinished(name,testResult) = 
-                Runner.onFinishedToString name testResult |> testOutputHelper.WriteLine
+                Runner.onFinishedToString name testResult |> safeWriteLine testOutputHelper
         }
 
     let private throwingRunner (testOutputHelper: ITestOutputHelper) =
         { new IRunner with
             member __.OnStartFixture t =
-                testOutputHelper.WriteLine (Runner.onStartFixtureToString t)
+                safeWriteLine testOutputHelper (Runner.onStartFixtureToString t)
             member __.OnArguments (ntest,args, every) =
-                testOutputHelper.WriteLine (every ntest args)
+                safeWriteLine testOutputHelper (every ntest args)
             member __.OnShrink(args, everyShrink) =
-                testOutputHelper.WriteLine (everyShrink args)
+                safeWriteLine testOutputHelper (everyShrink args)
             member __.OnFinished(name,testResult) = 
                 match testResult with
-                | TestResult.Passed _ -> testOutputHelper.WriteLine (Runner.onFinishedToString name testResult)
+                | TestResult.Passed _ -> safeWriteLine testOutputHelper (Runner.onFinishedToString name testResult)
                 | _ -> failwithf "%s" (Runner.onFinishedToString name testResult)
         }
 

src/FsCheck.Xunit/PropertyAttribute.fs

@@ -80,6 +80,16 @@ module internal PropertyConfig =
         { Rnd = Rnd (seed,gamma); Size = size }
 
     let toConfig (output : TestOutputHelper) propertyConfig =
+        // Helper to safely write to output, handling case where test may have completed
+        let safeWriteLine (message: string) =
+            try
+                output.WriteLine(message)
+            with
+            | :? InvalidOperationException -> 
+                // Test has completed, TestOutputHelper is no longer active
+                // Silently ignore as this is expected when closures outlive test lifetime
+                ()
+
         Config.Default
               .WithReplay(
                   propertyConfig.Replay
@@ -100,13 +110,13 @@ module internal PropertyConfig =
               .WithRunner(XunitRunner())
               .WithEvery(
                   if propertyConfig.Verbose |> Option.exists id then 
-                      fun n args -> output.WriteLine (Config.Verbose.Every n args); ""
+                      fun n args -> safeWriteLine (Config.Verbose.Every n args); ""
                   else 
                       Config.Quick.Every
               )
               .WithEveryShrink(
                   if propertyConfig.Verbose |> Option.exists id then 
-                      fun args -> output.WriteLine (Config.Verbose.EveryShrink args); ""
+                      fun args -> safeWriteLine (Config.Verbose.EveryShrink args); ""
                   else 
                       Config.Quick.EveryShrink
               )

src/FsCheck.Xunit/Runner.fs

@@ -1,20 +1,31 @@
 namespace FsCheck.Xunit
 
 open FsCheck
+open System
 
 /// A runner for FsCheck (i.e. that you can use as Config.Runner) which outputs
 /// to Xunit's given ITestOutputHelper.
 /// For example, { Config.QuickThrowOnFailure with Runner = TestOutputRunner(output) }
 type TestOutputRunner(output: Xunit.Abstractions.ITestOutputHelper) =
+    // Helper to safely write to output, handling case where test may have completed
+    let safeWriteLine (message: string) =
+        try
+            output.WriteLine(message)
+        with
+        | :? InvalidOperationException -> 
+            // Test has completed, TestOutputHelper is no longer active
+            // Silently ignore as this is expected when runner outlives test lifetime
+            ()
+
     interface IRunner with
         member _.OnStartFixture t =
-            output.WriteLine (Runner.onStartFixtureToString t)
+            safeWriteLine (Runner.onStartFixtureToString t)
         member _.OnArguments (ntest, args, every) =
-            output.WriteLine (every ntest args)
+            safeWriteLine (every ntest args)
         member _.OnShrink(args, everyShrink) =
-            output.WriteLine (everyShrink args)
+            safeWriteLine (everyShrink args)
         member _.OnFinished(name,testResult) =
             let resultText = Runner.onFinishedToString name testResult
             match testResult with
-            | TestResult.Passed _ -> resultText |> output.WriteLine
+            | TestResult.Passed _ -> resultText |> safeWriteLine
             | _ -> failwithf "%s" resultText

tests/FsCheck.Test.CSharp/FsCheck.Test.CSharp.csproj

@@ -6,4 +6,17 @@
         <IsPackable>false</IsPackable>
     </PropertyGroup>
 
+    <ItemGroup>
+        <ProjectReference Include="../../src/FsCheck.Xunit/FsCheck.Xunit.fsproj" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <PackageReference Include="xunit.core" />
+        <PackageReference Include="Microsoft.NET.Test.Sdk" />
+        <PackageReference Include="xunit.runner.visualstudio">
+          <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+          <PrivateAssets>all</PrivateAssets>
+        </PackageReference>
+    </ItemGroup>
+
 </Project>

tests/FsCheck.Test.CSharp/TestOutputHelperLifetimeTests.cs

@@ -0,0 +1,54 @@
+using Xunit;
+using Xunit.Abstractions;
+
+namespace FsCheck.Test.CSharp
+{
+    /// <summary>
+    /// Reproduction test for GitHub issue: Lifetime problem with Xunit: InvalidOperationException: There is no currently active test.
+    /// This test class verifies that mixing Property and Fact tests with ITestOutputHelper doesn't cause lifetime issues.
+    /// </summary>
+    public class TestOutputHelperLifetimeTests
+    {
+        private readonly ITestOutputHelper _testOutputHelper;
+
+        public TestOutputHelperLifetimeTests(ITestOutputHelper testOutputHelper)
+        {
+            _testOutputHelper = testOutputHelper;
+        }
+
+        [FsCheck.Xunit.Property]
+        public void Test1(int x)
+        {
+            _testOutputHelper.WriteLine($"{nameof(Test1)}: {x}");
+        }
+
+        [Fact]
+        public void Test2()
+        {
+            _testOutputHelper.WriteLine($"{nameof(Test2)}");
+        }
+
+        [FsCheck.Xunit.Property]
+        public void Test3(string s)
+        {
+            _testOutputHelper.WriteLine($"{nameof(Test3)}: {s ?? "null"}");
+        }
+
+        [Fact]
+        public void Test4()
+        {
+            _testOutputHelper.WriteLine($"{nameof(Test4)}");
+        }
+
+        /// <summary>
+        /// This test specifically exercises the Every and EveryShrink callbacks by enabling Verbose mode.
+        /// These callbacks capture the TestOutputHelper in closures, which was the root cause of the lifetime issue.
+        /// </summary>
+        [FsCheck.Xunit.Property(Verbose = true, MaxTest = 5)]
+        public bool Test5_VerboseMode(int x, int y)
+        {
+            _testOutputHelper.WriteLine($"{nameof(Test5_VerboseMode)}: x={x}, y={y}");
+            return true; // Always pass
+        }
+    }
+}