feat: add NotDiscoverableAttribute to hide tests from discovery

TUnit.Core/Attributes/TestMetadata/NotDiscoverableAttribute.cs

@@ -0,0 +1,100 @@
+using TUnit.Core.Interfaces;
+
+namespace TUnit.Core;
+
+/// <summary>
+/// Specifies that a test method, test class, or assembly should be hidden from test discovery/explorer.
+/// </summary>
+/// <remarks>
+/// <para>
+/// When applied to a test method, class, or assembly, the NotDiscoverableAttribute prevents the test(s)
+/// from appearing in test explorers and IDE test runners, while still allowing them to execute normally
+/// when run via filters or direct invocation.
+/// </para>
+/// <para>
+/// This is useful for infrastructure tests, internal helpers, or tests that should only be run
+/// as dependencies of other tests.
+/// </para>
+/// </remarks>
+/// <example>
+/// <code>
+/// // Simple usage - hide test from explorer
+/// [Test]
+/// [NotDiscoverable]
+/// public void InfrastructureSetupTest()
+/// {
+///     // This test will not appear in test explorer but can still be executed
+/// }
+///
+/// // With reason for documentation
+/// [Test]
+/// [NotDiscoverable("Internal fixture helper - not meant to be run directly")]
+/// public void SharedFixtureSetup()
+/// {
+///     // Hidden from discovery
+/// }
+///
+/// // Conditional hiding via inheritance
+/// public class NotDiscoverableOnCIAttribute : NotDiscoverableAttribute
+/// {
+///     public NotDiscoverableOnCIAttribute() : base("Hidden on CI") { }
+///
+///     public override Task&lt;bool&gt; ShouldHide(TestRegisteredContext context)
+///     {
+///         return Task.FromResult(Environment.GetEnvironmentVariable("CI") == "true");
+///     }
+/// }
+/// </code>
+/// </example>
+[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class | AttributeTargets.Assembly, AllowMultiple = false, Inherited = true)]
+public class NotDiscoverableAttribute : TUnitAttribute, ITestRegisteredEventReceiver
+{
+    /// <summary>
+    /// Gets the reason why this test is hidden from discovery.
+    /// </summary>
+    public string? Reason { get; }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="NotDiscoverableAttribute"/> class.
+    /// </summary>
+    public NotDiscoverableAttribute()
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="NotDiscoverableAttribute"/> class with a reason.
+    /// </summary>
+    /// <param name="reason">The reason why this test is hidden from discovery.</param>
+    public NotDiscoverableAttribute(string reason)
+    {
+        Reason = reason;
+    }
+
+    /// <inheritdoc />
+    public int Order => int.MinValue;
+
+    /// <inheritdoc />
+    public async ValueTask OnTestRegistered(TestRegisteredContext context)
+    {
+        if (await ShouldHide(context))
+        {
+            context.TestContext.IsNotDiscoverable = true;
+        }
+    }
+
+    /// <summary>
+    /// Determines whether the test should be hidden from discovery.
+    /// </summary>
+    /// <param name="context">The test context containing information about the test being registered.</param>
+    /// <returns>
+    /// A task that represents the asynchronous operation.
+    /// The task result is true if the test should be hidden; otherwise, false.
+    /// </returns>
+    /// <remarks>
+    /// Can be overridden in derived classes to implement conditional hiding logic
+    /// based on specific conditions or criteria.
+    ///
+    /// The default implementation always returns true, meaning the test will always be hidden.
+    /// </remarks>
+    public virtual Task<bool> ShouldHide(TestRegisteredContext context) => Task.FromResult(true);
+}

TUnit.Core/Interfaces/ITestExecution.cs

@@ -107,6 +107,13 @@ public interface ITestExecution
     /// </summary>
     bool ReportResult { get; set; }
 
+    /// <summary>
+    /// Gets or sets whether the test should be hidden from test discovery/explorer.
+    /// Defaults to false. Set to true to hide the test from discovery notifications
+    /// while still allowing it to execute when run directly.
+    /// </summary>
+    bool IsNotDiscoverable { get; set; }
+
     /// <summary>
     /// Links an external cancellation token to this test's execution token.
     /// Useful for coordinating cancellation across multiple operations or tests.

TUnit.Core/TestContext.Execution.cs

@@ -22,6 +22,7 @@ public partial class TestContext
     internal Func<TestContext, Exception, int, Task<bool>>? RetryFunc { get; set; }
     internal IHookExecutor? CustomHookExecutor { get; set; }
     internal bool ReportResult { get; set; } = true;
+    internal bool IsNotDiscoverable { get; set; }
 
     // Explicit interface implementations for ITestExecution
     TestPhase ITestExecution.Phase => Phase;
@@ -62,6 +63,11 @@ bool ITestExecution.ReportResult
         get => ReportResult;
         set => ReportResult = value;
     }
+    bool ITestExecution.IsNotDiscoverable
+    {
+        get => IsNotDiscoverable;
+        set => IsNotDiscoverable = value;
+    }
 
     void ITestExecution.OverrideResult(TestState state, string reason) => OverrideResult(state, reason);
     void ITestExecution.AddLinkedCancellationToken(CancellationToken cancellationToken) => AddLinkedCancellationToken(cancellationToken);

TUnit.Engine/TUnitMessageBus.cs

@@ -23,6 +23,11 @@ internal class TUnitMessageBus(IExtension extension, ICommandLineOptions command
 
     public async ValueTask Discovered(TestContext testContext)
     {
+        if (testContext.IsNotDiscoverable)
+        {
+            return;
+        }
+
         await context.MessageBus.PublishAsync(this, new TestNodeUpdateMessage(
             sessionUid: _sessionSessionUid,
             testNode: testContext.ToTestNode(DiscoveredTestNodeStateProperty.CachedInstance)

TUnit.PublicAPI/Tests.Core_Library_Has_No_API_Changes.DotNet10_0.verified.txt

@@ -1004,6 +1004,16 @@ namespace
         public override int GetHashCode() { }
         protected virtual bool PrintMembers(.StringBuilder stringBuilder) { }
     }
+    [(.Assembly | .Class | .Method, AllowMultiple=false, Inherited=true)]
+    public class NotDiscoverableAttribute : .TUnitAttribute, ., .
+    {
+        public NotDiscoverableAttribute() { }
+        public NotDiscoverableAttribute(string reason) { }
+        public int Order { get; }
+        public string? Reason { get; }
+        public . OnTestRegistered(.TestRegisteredContext context) { }
+        public virtual .<bool> ShouldHide(.TestRegisteredContext context) { }
+    }
     [(.Assembly | .Class | .Method)]
     public class NotInParallelAttribute : .SingleTUnitAttribute, .IScopedAttribute, ., .
     {
@@ -2412,6 +2422,7 @@ namespace .Interfaces
         .CancellationToken CancellationToken { get; }
         int CurrentRetryAttempt { get; }
         .? CustomHookExecutor { get; set; }
+        bool IsNotDiscoverable { get; set; }
         .TestPhase Phase { get; }
         bool ReportResult { get; set; }
         .TestResult? Result { get; }

TUnit.PublicAPI/Tests.Core_Library_Has_No_API_Changes.DotNet8_0.verified.txt

@@ -1004,6 +1004,16 @@ namespace
         public override int GetHashCode() { }
         protected virtual bool PrintMembers(.StringBuilder stringBuilder) { }
     }
+    [(.Assembly | .Class | .Method, AllowMultiple=false, Inherited=true)]
+    public class NotDiscoverableAttribute : .TUnitAttribute, ., .
+    {
+        public NotDiscoverableAttribute() { }
+        public NotDiscoverableAttribute(string reason) { }
+        public int Order { get; }
+        public string? Reason { get; }
+        public . OnTestRegistered(.TestRegisteredContext context) { }
+        public virtual .<bool> ShouldHide(.TestRegisteredContext context) { }
+    }
     [(.Assembly | .Class | .Method)]
     public class NotInParallelAttribute : .SingleTUnitAttribute, .IScopedAttribute, ., .
     {
@@ -2412,6 +2422,7 @@ namespace .Interfaces
         .CancellationToken CancellationToken { get; }
         int CurrentRetryAttempt { get; }
         .? CustomHookExecutor { get; set; }
+        bool IsNotDiscoverable { get; set; }
         .TestPhase Phase { get; }
         bool ReportResult { get; set; }
         .TestResult? Result { get; }

TUnit.PublicAPI/Tests.Core_Library_Has_No_API_Changes.DotNet9_0.verified.txt

@@ -1004,6 +1004,16 @@ namespace
         public override int GetHashCode() { }
         protected virtual bool PrintMembers(.StringBuilder stringBuilder) { }
     }
+    [(.Assembly | .Class | .Method, AllowMultiple=false, Inherited=true)]
+    public class NotDiscoverableAttribute : .TUnitAttribute, ., .
+    {
+        public NotDiscoverableAttribute() { }
+        public NotDiscoverableAttribute(string reason) { }
+        public int Order { get; }
+        public string? Reason { get; }
+        public . OnTestRegistered(.TestRegisteredContext context) { }
+        public virtual .<bool> ShouldHide(.TestRegisteredContext context) { }
+    }
     [(.Assembly | .Class | .Method)]
     public class NotInParallelAttribute : .SingleTUnitAttribute, .IScopedAttribute, ., .
     {
@@ -2412,6 +2422,7 @@ namespace .Interfaces
         .CancellationToken CancellationToken { get; }
         int CurrentRetryAttempt { get; }
         .? CustomHookExecutor { get; set; }
+        bool IsNotDiscoverable { get; set; }
         .TestPhase Phase { get; }
         bool ReportResult { get; set; }
         .TestResult? Result { get; }

TUnit.PublicAPI/Tests.Core_Library_Has_No_API_Changes.Net4_7.verified.txt

@@ -967,6 +967,16 @@ namespace
         public override int GetHashCode() { }
         protected virtual bool PrintMembers(.StringBuilder stringBuilder) { }
     }
+    [(.Assembly | .Class | .Method, AllowMultiple=false, Inherited=true)]
+    public class NotDiscoverableAttribute : .TUnitAttribute, ., .
+    {
+        public NotDiscoverableAttribute() { }
+        public NotDiscoverableAttribute(string reason) { }
+        public int Order { get; }
+        public string? Reason { get; }
+        public . OnTestRegistered(.TestRegisteredContext context) { }
+        public virtual .<bool> ShouldHide(.TestRegisteredContext context) { }
+    }
     [(.Assembly | .Class | .Method)]
     public class NotInParallelAttribute : .SingleTUnitAttribute, .IScopedAttribute, ., .
     {
@@ -2342,6 +2352,7 @@ namespace .Interfaces
         .CancellationToken CancellationToken { get; }
         int CurrentRetryAttempt { get; }
         .? CustomHookExecutor { get; set; }
+        bool IsNotDiscoverable { get; set; }
         .TestPhase Phase { get; }
         bool ReportResult { get; set; }
         .TestResult? Result { get; }

TUnit.TestProject/NotDiscoverableTests.cs

@@ -0,0 +1,61 @@
+namespace TUnit.TestProject;
+
+public class NotDiscoverableTests
+{
+    [Test]
+    [NotDiscoverable]
+    public void Test_WithNotDiscoverable_ShouldNotAppearInDiscovery()
+    {
+        // This test should execute but not appear in test explorer
+    }
+
+    [Test]
+    [NotDiscoverable("Infrastructure test")]
+    public void Test_WithNotDiscoverableAndReason_ShouldNotAppearInDiscovery()
+    {
+        // This test should execute but not appear in test explorer
+    }
+
+    [Test]
+    public void Test_WithoutNotDiscoverable_ShouldAppearInDiscovery()
+    {
+        // This test should appear normally in test explorer
+    }
+}
+
+[NotDiscoverable]
+public class NotDiscoverableClassTests
+{
+    [Test]
+    public void Test_InNotDiscoverableClass_ShouldNotAppearInDiscovery()
+    {
+        // All tests in this class should be hidden from discovery
+    }
+
+    [Test]
+    public void AnotherTest_InNotDiscoverableClass_ShouldNotAppearInDiscovery()
+    {
+        // All tests in this class should be hidden from discovery
+    }
+}
+
+public class ConditionalNotDiscoverableAttribute : NotDiscoverableAttribute
+{
+    public ConditionalNotDiscoverableAttribute() : base("Conditionally hidden") { }
+
+    public override Task<bool> ShouldHide(TestRegisteredContext context)
+    {
+        // Only hide if environment variable is set
+        return Task.FromResult(Environment.GetEnvironmentVariable("HIDE_TEST") == "true");
+    }
+}
+
+public class ConditionalNotDiscoverableTests
+{
+    [Test]
+    [ConditionalNotDiscoverable]
+    public void Test_WithConditionalNotDiscoverable_HidesBasedOnCondition()
+    {
+        // This test is hidden only when HIDE_TEST=true
+    }
+}