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

@@ -9,26 +9,26 @@ module private Helper =
     let private runner (testOutputHelper: ITestOutputHelper) =
         { new IRunner with
             member __.OnStartFixture t =
-                Runner.onStartFixtureToString t |> testOutputHelper.WriteLine
+                Runner.onStartFixtureToString t |> Helpers.safeWriteLine testOutputHelper
             member __.OnArguments (ntest,args, every) =
-                every ntest args |> testOutputHelper.WriteLine
+                every ntest args |> Helpers.safeWriteLine testOutputHelper
             member __.OnShrink(args, everyShrink) =
-                everyShrink args |> testOutputHelper.WriteLine
+                everyShrink args |> Helpers.safeWriteLine testOutputHelper
             member __.OnFinished(name,testResult) = 
-                Runner.onFinishedToString name testResult |> testOutputHelper.WriteLine
+                Runner.onFinishedToString name testResult |> Helpers.safeWriteLine testOutputHelper
         }
 
     let private throwingRunner (testOutputHelper: ITestOutputHelper) =
         { new IRunner with
             member __.OnStartFixture t =
-                testOutputHelper.WriteLine (Runner.onStartFixtureToString t)
+                Helpers.safeWriteLine testOutputHelper (Runner.onStartFixtureToString t)
             member __.OnArguments (ntest,args, every) =
-                testOutputHelper.WriteLine (every ntest args)
+                Helpers.safeWriteLine testOutputHelper (every ntest args)
             member __.OnShrink(args, everyShrink) =
-                testOutputHelper.WriteLine (everyShrink args)
+                Helpers.safeWriteLine testOutputHelper (everyShrink args)
             member __.OnFinished(name,testResult) = 
                 match testResult with
-                | TestResult.Passed _ -> testOutputHelper.WriteLine (Runner.onFinishedToString name testResult)
+                | TestResult.Passed _ -> Helpers.safeWriteLine testOutputHelper (Runner.onFinishedToString name testResult)
                 | _ -> failwithf "%s" (Runner.onFinishedToString name testResult)
         }
 

src/FsCheck.Xunit/FsCheck.Xunit.fsproj

@@ -14,6 +14,7 @@
     </PropertyGroup>
     <ItemGroup>
         <Compile Include="AssemblyInfo.fs"/>
+        <Compile Include="Helpers.fs"/>
         <Compile Include="Runner.fs"/>
         <Compile Include="PropertyAttribute.fs"/>
         <Compile Include="CheckExtensions.fs"/>

src/FsCheck.Xunit/Helpers.fs

@@ -0,0 +1,19 @@
+namespace FsCheck.Xunit
+
+open System
+open Xunit.Abstractions
+
+module internal Helpers =
+    /// <summary>
+    /// Safely writes to a TestOutputHelper, handling cases where the test may have completed
+    /// and the helper is no longer active. This prevents InvalidOperationException when
+    /// closures that capture the TestOutputHelper are called after the test lifetime ends.
+    /// </summary>
+    let safeWriteLine (output: ITestOutputHelper) (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
+            ()

src/FsCheck.Xunit/PropertyAttribute.fs

@@ -100,13 +100,13 @@ 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 -> Helpers.safeWriteLine output (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 -> Helpers.safeWriteLine output (Config.Verbose.EveryShrink args); ""
                   else 
                       Config.Quick.EveryShrink
               )

src/FsCheck.Xunit/Runner.fs

@@ -1,20 +1,21 @@
 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) =
     interface IRunner with
         member _.OnStartFixture t =
-            output.WriteLine (Runner.onStartFixtureToString t)
+            Helpers.safeWriteLine output (Runner.onStartFixtureToString t)
         member _.OnArguments (ntest, args, every) =
-            output.WriteLine (every ntest args)
+            Helpers.safeWriteLine output (every ntest args)
         member _.OnShrink(args, everyShrink) =
-            output.WriteLine (everyShrink args)
+            Helpers.safeWriteLine output (everyShrink args)
         member _.OnFinished(name,testResult) =
             let resultText = Runner.onFinishedToString name testResult
             match testResult with
-            | TestResult.Passed _ -> resultText |> output.WriteLine
+            | TestResult.Passed _ -> resultText |> Helpers.safeWriteLine output
             | _ -> failwithf "%s" resultText

tests/FsCheck.Test/Fscheck.XUnit/PropertyAttributeTests.fs

@@ -91,3 +91,36 @@ module ``when type implements IAsyncLifetime`` =
         [<Property(MaxTest = 1)>]
         member this.``then InitializeAsync() is invoked``() =
             executed = true
+
+/// 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.
+module ``when mixing Property and Fact tests with ITestOutputHelper`` =
+    open Xunit.Abstractions
+
+    type TestOutputHelperLifetimeTests(output: ITestOutputHelper) =
+
+        [<Property>]
+        member _.``Property test with parameter writes to output`` (x: int) =
+            output.WriteLine($"Property test with parameter: {x}")
+            true
+
+        [<Fact>]
+        member _.``Fact test writes to output`` () =
+            output.WriteLine("Fact test")
+
+        [<Property>]
+        member _.``Property test with string parameter writes to output`` (s: string) =
+            let str = if isNull s then "null" else s
+            output.WriteLine($"Property test with string: {str}")
+            true
+
+        [<Fact>]
+        member _.``Another fact test writes to output`` () =
+            output.WriteLine("Another fact test")
+
+        /// 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.
+        [<Property(Verbose = true, MaxTest = 5)>]
+        member _.``Verbose property test exercises Every and EveryShrink callbacks`` (x: int) (y: int) =
+            output.WriteLine($"Verbose mode test: x={x}, y={y}")
+            true