perf: replace object locks with Lock type for efficient synchronization

TUnit.Core/AotCompatibility/GenericTestRegistry.cs

@@ -12,7 +12,7 @@ public static class GenericTestRegistry
     private static readonly ConcurrentDictionary<GenericMethodKey, MethodInfo> _compiledMethods = new();
     private static readonly ConcurrentDictionary<Type, HashSet<Type[]>> _registeredCombinations = new();
     private static readonly ConcurrentDictionary<GenericMethodKey, Delegate> _directInvocationDelegates = new();
-    private static readonly object _combinationsLock = new();
+    private static readonly Lock _combinationsLock = new();
 
     /// <summary>
     /// Registers a pre-compiled generic method instance.

TUnit.Core/Context.cs

@@ -29,28 +29,20 @@ TestContext.Current as Context
 
     // Console interceptor line buffers for partial writes (Console.Write without newline)
     // These are stored per-context to prevent output mixing between parallel tests
-    // Using Lazy<T> for thread-safe initialization
-    private readonly Lazy<StringBuilder> _consoleStdOutLineBuffer = new(() => new StringBuilder());
-    private readonly Lazy<StringBuilder> _consoleStdErrLineBuffer = new(() => new StringBuilder());
-    private readonly object _consoleStdOutBufferLock = new();
-    private readonly object _consoleStdErrBufferLock = new();
+    // ConsoleLineBuffer uses Lock internally for efficient synchronization
+    private readonly ConsoleLineBuffer _consoleStdOutLineBuffer = new();
+    private readonly ConsoleLineBuffer _consoleStdErrLineBuffer = new();
 
     [field: AllowNull, MaybeNull]
     public TextWriter OutputWriter => field ??= new ConcurrentStringWriter(_outputBuilder, _outputLock);
 
     [field: AllowNull, MaybeNull]
     public TextWriter ErrorOutputWriter => field ??= new ConcurrentStringWriter(_errorOutputBuilder, _errorOutputLock);
 
-    // Internal accessors for console interceptor line buffers with thread safety
-    internal (StringBuilder Buffer, object Lock) GetConsoleStdOutLineBuffer()
-    {
-        return (_consoleStdOutLineBuffer.Value, _consoleStdOutBufferLock);
-    }
+    // Internal accessors for console interceptor line buffers
+    internal ConsoleLineBuffer ConsoleStdOutLineBuffer => _consoleStdOutLineBuffer;
 
-    internal (StringBuilder Buffer, object Lock) GetConsoleStdErrLineBuffer()
-    {
-        return (_consoleStdErrLineBuffer.Value, _consoleStdErrBufferLock);
-    }
+    internal ConsoleLineBuffer ConsoleStdErrLineBuffer => _consoleStdErrLineBuffer;
 
     internal Context(Context? parent)
     {

TUnit.Core/Logging/ConsoleLineBuffer.cs

@@ -0,0 +1,100 @@
+using System.Text;
+
+namespace TUnit.Core.Logging;
+
+/// <summary>
+/// Thread-safe line buffer for console interceptor partial writes.
+/// Uses <see cref="Lock"/> internally for efficient synchronization.
+/// Each context owns its own buffer, preventing output mixing between parallel tests.
+/// </summary>
+internal sealed class ConsoleLineBuffer
+{
+    private readonly Lazy<StringBuilder> _buffer = new(() => new StringBuilder());
+    private readonly Lock _lock = new();
+
+    /// <summary>
+    /// Appends a string to the buffer.
+    /// </summary>
+    internal void Append(string value)
+    {
+        lock (_lock)
+        {
+            _buffer.Value.Append(value);
+        }
+    }
+
+    /// <summary>
+    /// Appends a single character to the buffer.
+    /// </summary>
+    internal void Append(char value)
+    {
+        lock (_lock)
+        {
+            _buffer.Value.Append(value);
+        }
+    }
+
+    /// <summary>
+    /// Appends a range of characters to the buffer.
+    /// </summary>
+    internal void Append(char[] buffer, int index, int count)
+    {
+        lock (_lock)
+        {
+            _buffer.Value.Append(buffer, index, count);
+        }
+    }
+
+    /// <summary>
+    /// Drains all buffered content and clears the buffer.
+    /// </summary>
+    internal string Drain()
+    {
+        lock (_lock)
+        {
+            var buf = _buffer.Value;
+            var result = buf.ToString();
+            buf.Clear();
+            return result;
+        }
+    }
+
+    /// <summary>
+    /// If the buffer has content, appends <paramref name="value"/> to it, drains, and returns the combined result.
+    /// If the buffer is empty, returns <paramref name="value"/> unchanged.
+    /// </summary>
+    internal string? AppendAndDrain(string? value)
+    {
+        lock (_lock)
+        {
+            var buf = _buffer.Value;
+            if (buf.Length > 0)
+            {
+                buf.Append(value);
+                value = buf.ToString();
+                buf.Clear();
+            }
+        }
+
+        return value;
+    }
+
+    /// <summary>
+    /// If the buffer has content, drains and returns it. Otherwise returns <c>null</c>.
+    /// </summary>
+    internal string? FlushIfNonEmpty()
+    {
+        lock (_lock)
+        {
+            var buf = _buffer.Value;
+            if (buf.Length > 0)
+            {
+                var result = buf.ToString();
+                buf.Clear();
+                return result;
+            }
+
+            return null;
+        }
+    }
+}

TUnit.Engine.Tests/ThreadSafeOutput.cs

@@ -2,7 +2,7 @@
 
 public static class ThreadSafeOutput
 {
-    private static readonly object OutputLock = new();
+    private static readonly Lock OutputLock = new();
 
     public static void WriteLine(string value)
     {

TUnit.Engine/Logging/OptimizedConsoleInterceptor.cs

@@ -23,10 +23,11 @@ internal abstract class OptimizedConsoleInterceptor : TextWriter
     protected abstract LogLevel SinkLogLevel { get; }
 
     /// <summary>
-    /// Gets the line buffer and lock from the current context.
+    /// Gets the line buffer from the current context.
     /// This ensures each test has its own buffer, preventing output mixing between parallel tests.
+    /// Locking is handled internally by <see cref="ConsoleLineBuffer"/> using the efficient Lock type.
     /// </summary>
-    protected abstract (StringBuilder Buffer, object Lock) GetLineBuffer();
+    protected abstract ConsoleLineBuffer GetLineBuffer();
 
     private protected abstract TextWriter GetOriginalOut();
 
@@ -64,30 +65,13 @@ public override ValueTask DisposeAsync()
 
     public override void Flush()
     {
-        // Flush any buffered partial line
-        var (buffer, bufferLock) = GetLineBuffer();
-        lock (bufferLock)
-        {
-            if (buffer.Length > 0)
-            {
-                RouteToSinks(buffer.ToString());
-                buffer.Clear();
-            }
-        }
+        var content = GetLineBuffer().FlushIfNonEmpty();
+        RouteToSinks(content);
     }
 
     public override async Task FlushAsync()
     {
-        var (buffer, bufferLock) = GetLineBuffer();
-        string? content = null;
-        lock (bufferLock)
-        {
-            if (buffer.Length > 0)
-            {
-                content = buffer.ToString();
-                buffer.Clear();
-            }
-        }
+        var content = GetLineBuffer().FlushIfNonEmpty();
         if (content != null)
         {
             await RouteToSinksAsync(content).ConfigureAwait(false);
@@ -96,12 +80,12 @@ public override async Task FlushAsync()
 
     // Write methods - buffer partial writes until we get a complete line
     public override void Write(bool value) => Write(value.ToString());
-    public override void Write(char value) => BufferChar(value);
+    public override void Write(char value) => GetLineBuffer().Append(value);
     public override void Write(char[]? buffer)
     {
         if (buffer != null)
         {
-            BufferChars(buffer, 0, buffer.Length);
+            GetLineBuffer().Append(buffer, 0, buffer.Length);
         }
     }
     public override void Write(decimal value) => Write(value.ToString());
@@ -113,49 +97,20 @@ public override void Write(char[]? buffer)
     public override void Write(string? value)
     {
         if (value == null) return;
-        var (buffer, bufferLock) = GetLineBuffer();
-        lock (bufferLock)
-        {
-            buffer.Append(value);
-        }
+        GetLineBuffer().Append(value);
     }
     public override void Write(uint value) => Write(value.ToString());
     public override void Write(ulong value) => Write(value.ToString());
-    public override void Write(char[] buffer, int index, int count) => BufferChars(buffer, index, count);
+    public override void Write(char[] buffer, int index, int count) => GetLineBuffer().Append(buffer, index, count);
     public override void Write(string format, object? arg0) => Write(string.Format(format, arg0));
     public override void Write(string format, object? arg0, object? arg1) => Write(string.Format(format, arg0, arg1));
     public override void Write(string format, object? arg0, object? arg1, object? arg2) => Write(string.Format(format, arg0, arg1, arg2));
     public override void Write(string format, params object?[] arg) => Write(string.Format(format, arg));
 
-    private void BufferChar(char value)
-    {
-        var (buffer, bufferLock) = GetLineBuffer();
-        lock (bufferLock)
-        {
-            buffer.Append(value);
-        }
-    }
-
-    private void BufferChars(char[] buffer, int index, int count)
-    {
-        var (lineBuffer, bufferLock) = GetLineBuffer();
-        lock (bufferLock)
-        {
-            lineBuffer.Append(buffer, index, count);
-        }
-    }
-
     // WriteLine methods - flush buffer and route complete line to sinks
     public override void WriteLine()
     {
-        var (buffer, bufferLock) = GetLineBuffer();
-        string line;
-        lock (bufferLock)
-        {
-            line = buffer.ToString();
-            buffer.Clear();
-        }
-        RouteToSinks(line);
+        RouteToSinks(GetLineBuffer().Drain());
     }
 
     public override void WriteLine(bool value) => WriteLine(value.ToString());
@@ -172,16 +127,7 @@ public override void WriteLine()
     public override void WriteLine(string? value)
     {
         // Prepend any buffered content
-        var (buffer, bufferLock) = GetLineBuffer();
-        lock (bufferLock)
-        {
-            if (buffer.Length > 0)
-            {
-                buffer.Append(value);
-                value = buffer.ToString();
-                buffer.Clear();
-            }
-        }
+        value = GetLineBuffer().AppendAndDrain(value);
         RouteToSinks(value);
     }
 
@@ -210,16 +156,7 @@ public override async Task WriteLineAsync(char[] buffer, int index, int count)
 
     public override async Task WriteLineAsync(string? value)
     {
-        var (buffer, bufferLock) = GetLineBuffer();
-        lock (bufferLock)
-        {
-            if (buffer.Length > 0)
-            {
-                buffer.Append(value);
-                value = buffer.ToString();
-                buffer.Clear();
-            }
-        }
+        value = GetLineBuffer().AppendAndDrain(value);
         await RouteToSinksAsync(value).ConfigureAwait(false);
     }
 

TUnit.Engine/Logging/StandardErrorConsoleInterceptor.cs

@@ -1,4 +1,3 @@
-using System.Text;
 using TUnit.Core;
 using TUnit.Core.Logging;
 
@@ -12,7 +11,7 @@ internal class StandardErrorConsoleInterceptor : OptimizedConsoleInterceptor
 
     protected override LogLevel SinkLogLevel => LogLevel.Error;
 
-    protected override (StringBuilder Buffer, object Lock) GetLineBuffer() => Context.Current.GetConsoleStdErrLineBuffer();
+    protected override ConsoleLineBuffer GetLineBuffer() => Context.Current.ConsoleStdErrLineBuffer;
 
     static StandardErrorConsoleInterceptor()
     {

TUnit.Engine/Logging/StandardOutConsoleInterceptor.cs

@@ -1,4 +1,3 @@
-using System.Text;
 using TUnit.Core;
 using TUnit.Core.Logging;
 
@@ -12,7 +11,7 @@ internal class StandardOutConsoleInterceptor : OptimizedConsoleInterceptor
 
     protected override LogLevel SinkLogLevel => LogLevel.Information;
 
-    protected override (StringBuilder Buffer, object Lock) GetLineBuffer() => Context.Current.GetConsoleStdOutLineBuffer();
+    protected override ConsoleLineBuffer GetLineBuffer() => Context.Current.ConsoleStdOutLineBuffer;
 
     static StandardOutConsoleInterceptor()
     {

TUnit.Engine/Scheduling/ConstraintKeyScheduler.cs

@@ -38,7 +38,7 @@ public async ValueTask ExecuteTestsWithConstraintsAsync(
 
         // Track which constraint keys are currently in use
         var lockedKeys = new HashSet<string>();
-        var lockObject = new object();
+        var lockObject = new Lock();
 
         // Indexed structure for tests waiting for their constraint keys to become available
         var waitingTestIndex = new WaitingTestIndex();
@@ -122,7 +122,7 @@ private async Task WaitAndExecuteTestAsync(
         IReadOnlyList<string> constraintKeys,
         TaskCompletionSource<bool> startSignal,
         HashSet<string> lockedKeys,
-        object lockObject,
+        Lock lockObject,
         WaitingTestIndex waitingTestIndex,
         CancellationToken cancellationToken)
     {
@@ -142,7 +142,7 @@ private async Task ExecuteTestAndReleaseKeysAsync(
         AbstractExecutableTest test,
         IReadOnlyList<string> constraintKeys,
         HashSet<string> lockedKeys,
-        object lockObject,
+        Lock lockObject,
         WaitingTestIndex waitingTestIndex,
         CancellationToken cancellationToken)
     {

TUnit.Mocks.Http/MockHttpHandler.cs

@@ -11,7 +11,7 @@ namespace TUnit.Mocks.Http;
 public sealed class MockHttpHandler : HttpMessageHandler
 {
     private readonly List<RequestSetup> _setups = new();
-    private readonly object _setupsLock = new();
+    private readonly Lock _setupsLock = new();
     private readonly ConcurrentQueue<CapturedRequest> _requests = new();
     private HttpStatusCode _defaultStatusCode = HttpStatusCode.NotFound;
     private bool _throwOnUnmatched;

TUnit.Playwright/BrowserTest.cs

@@ -17,7 +17,7 @@ public BrowserTest(BrowserTypeLaunchOptions options)
     public IBrowser Browser { get; internal set; } = null!;
 
     private readonly List<IBrowserContext> _contexts = [];
-    private readonly object _contextsLock = new();
+    private readonly Lock _contextsLock = new();
     private readonly BrowserTypeLaunchOptions _options;
 
     public async Task<IBrowserContext> NewContext(BrowserNewContextOptions options)