Enhance test stability and readability in Enumerator tests

src/EventStore.Core.Tests/Services/Transport/Enumerators/Enumerator.StreamSubscription.CombinationTests.cs

@@ -57,6 +57,11 @@ public enum CheckpointType
 
 		private const int NumEventsToFallBehind = 3 * 32;
 
+		// Delay to wait for max age expiration in tests. Set to 2500ms (2.5 seconds) to account for
+		// timing variations, especially on Windows where expiration checks may not be perfectly synchronized.
+		// This reduces test flakiness by ensuring events are fully expired before verification.
+		private const int ExpirationDelayMs = 2500;
+
 		public static object[] TestCases = {
 			// NON-EXISTENT STREAM
 			CreateTestData(
@@ -687,8 +692,15 @@ private Task WriteMetadata(string metadata)
 		private Task MaxCount(long maxCount) => WriteMetadata(@$"{{""$maxCount"":{maxCount}}}");
 		private async Task ExpiredMaxAge()
 		{
+			// Set max age to 1 second - events older than this will be expired/truncated.
+			// Note: A max age of zero doesn't do anything, so we're forced to use at least 1 second.
 			await WriteMetadata(@"{""$maxAge"": 1 }"); // seconds
-			await Task.Delay(TimeSpan.FromMilliseconds(2000));
+
+			// Wait for events to expire. Using ExpirationDelayMs (2500ms) instead of the minimum 1001ms
+			// to account for timing variations, especially on Windows where expiration checks may
+			// not be perfectly synchronized. This reduces test flakiness by ensuring events are
+			// fully expired before the test proceeds to verify they're gone.
+			await Task.Delay(TimeSpan.FromMilliseconds(ExpirationDelayMs));
 		}
 
 		private Task ApplyTruncation()
@@ -890,6 +902,8 @@ public async Task enumeration_is_correct()
 				return;
 			}
 
+			// Verify subscription confirmation message. Store in variable to enable better error messages
+			// that include the test case name and actual type received, making debugging easier when tests fail.
 			var current = await sub.GetNext();
 			Assert.True(
 				current is SubscriptionConfirmation,
@@ -899,6 +913,8 @@ public async Task enumeration_is_correct()
 
 			_nextEventNumber = await ReadExpectedEvents(sub, _nextEventNumber, LastEventNumber);
 
+			// Verify caught-up message with descriptive error message for easier debugging.
+			// This helps identify which test case failed and what message type was received instead.
 			current = await sub.GetNext();
 			Assert.True(
 				current is CaughtUp,

src/EventStore.Core.Tests/TransactionLog/versioned_pattern_filenaming_strategy.cs

@@ -192,7 +192,8 @@ public void throws_for_incorrectly_formatted_filename()
 	}
 
 	[Test]
-	public void returns_correct_prefix_with_get_prefix_for() {
+	public void returns_correct_prefix_with_get_prefix_for()
+	{
 		var strategy = new VersionedPatternFileNamingStrategy(PathName, "chunk-");
 		Assert.AreEqual("chunk-", strategy.GetPrefixFor(null, null));
 		Assert.AreEqual("chunk-000000.", strategy.GetPrefixFor(0, null));

src/EventStore.Core.Tests/TransactionLog/when_chasing_a_chunked_transaction_log.cs

@@ -20,13 +20,16 @@ public static class LogRecordExtensions
 	public static void WriteWithLengthPrefixAndSuffixTo(this ILogRecord record, BinaryWriter writer)
 	{
 		var localWriter = new BufferWriterSlim<byte>();
-		try {
+		try
+		{
 			record.WriteTo(ref localWriter);
 
 			writer.Write(localWriter.WrittenCount);
 			writer.Write(localWriter.WrittenSpan);
 			writer.Write(localWriter.WrittenCount);
-		} finally {
+		}
+		finally
+		{
 			localWriter.Dispose();
 		}
 	}

src/EventStore.Core.Tests/TransactionLog/when_reading_physical_bytes_bulk_from_a_chunk.cs

@@ -38,39 +38,39 @@ public async Task a_read_on_new_file_can_be_performed()
 		chunk.MarkForDeletion();
 		chunk.WaitForDestroy(5000);
 	}
-/*
-        [Test]
-        public void a_read_on_scavenged_chunk_includes_map()
-        {
-            var chunk = TFChunk.CreateNew(GetFilePathFor("afile"), 200, 0, 0, isScavenged: true, inMem: false, unbuffered: false, writethrough: false);
-            chunk.CompleteScavenge(new [] {new PosMap(0, 0), new PosMap(1,1) }, false);
-            using (var reader = chunk.AcquireRawReader())
-            {
-                var buffer = new byte[1024];
-                var result = reader.ReadNextBytes(1024, buffer);
-                Assert.IsFalse(result.IsEOF);
-                Assert.AreEqual(ChunkHeader.Size + ChunkHeader.Size + 2 * PosMap.FullSize, result.BytesRead);
-            }
-            chunk.MarkForDeletion();
-            chunk.WaitForDestroy(5000);
-        }
+	/*
+			[Test]
+			public void a_read_on_scavenged_chunk_includes_map()
+			{
+				var chunk = TFChunk.CreateNew(GetFilePathFor("afile"), 200, 0, 0, isScavenged: true, inMem: false, unbuffered: false, writethrough: false);
+				chunk.CompleteScavenge(new [] {new PosMap(0, 0), new PosMap(1,1) }, false);
+				using (var reader = chunk.AcquireRawReader())
+				{
+					var buffer = new byte[1024];
+					var result = reader.ReadNextBytes(1024, buffer);
+					Assert.IsFalse(result.IsEOF);
+					Assert.AreEqual(ChunkHeader.Size + ChunkHeader.Size + 2 * PosMap.FullSize, result.BytesRead);
+				}
+				chunk.MarkForDeletion();
+				chunk.WaitForDestroy(5000);
+			}
 
-        [Test]
-        public void a_read_past_end_of_completed_chunk_does_include_header_or_footer()
-        {
-            var chunk = TFChunk.CreateNew(GetFilePathFor("File1"), 300, 0, 0, isScavenged: false, inMem: false, unbuffered: false, writethrough: false);
-            chunk.Complete();
-            using (var reader = chunk.AcquireRawReader())
-            {
-                var buffer = new byte[1024];
-                var result = reader.ReadNextBytes(1024, buffer);
-                Assert.IsTrue(result.IsEOF);
-                Assert.AreEqual(ChunkHeader.Size + ChunkFooter.Size, result.BytesRead); //just header + footer = 256
-            }
-            chunk.MarkForDeletion();
-            chunk.WaitForDestroy(5000);
-        }
-*/
+			[Test]
+			public void a_read_past_end_of_completed_chunk_does_include_header_or_footer()
+			{
+				var chunk = TFChunk.CreateNew(GetFilePathFor("File1"), 300, 0, 0, isScavenged: false, inMem: false, unbuffered: false, writethrough: false);
+				chunk.Complete();
+				using (var reader = chunk.AcquireRawReader())
+				{
+					var buffer = new byte[1024];
+					var result = reader.ReadNextBytes(1024, buffer);
+					Assert.IsTrue(result.IsEOF);
+					Assert.AreEqual(ChunkHeader.Size + ChunkFooter.Size, result.BytesRead); //just header + footer = 256
+				}
+				chunk.MarkForDeletion();
+				chunk.WaitForDestroy(5000);
+			}
+	*/
 
 	[Test]
 	public async Task if_asked_for_more_than_buffer_size_will_only_read_buffer_size()

src/EventStore.Core.Tests/TransactionLog/when_writing_an_existing_chunked_transaction_file_with_checksum.cs

@@ -68,7 +68,9 @@ public async Task a_record_can_be_written()
 		await using var filestream = File.Open(filename,
 			new FileStreamOptions
 			{
-				Mode = FileMode.Open, Access = FileAccess.Read, Options = FileOptions.Asynchronous
+				Mode = FileMode.Open,
+				Access = FileAccess.Read,
+				Options = FileOptions.Asynchronous
 			});
 		filestream.Seek(ChunkHeader.Size + 137 + sizeof(int), SeekOrigin.Begin);
 		var recordLength = filestream.Length - filestream.Position;

src/EventStore.Core.Tests/TransactionLog/when_writing_an_existing_chunked_transaction_file_with_checksum_and_data_bigger_than_buffer.cs

@@ -73,7 +73,9 @@ public async Task a_record_can_be_written()
 		await using var filestream = File.Open(filename,
 			new FileStreamOptions
 			{
-				Mode = FileMode.Open, Access = FileAccess.Read, Options = FileOptions.Asynchronous
+				Mode = FileMode.Open,
+				Access = FileAccess.Read,
+				Options = FileOptions.Asynchronous
 			});
 		filestream.Seek(ChunkHeader.Size + 137 + sizeof(int), SeekOrigin.Begin);
 		var recordLength = filestream.Length - filestream.Position;

src/EventStore.Core.Tests/TransactionLog/when_writing_an_existing_chunked_transaction_file_with_not_enough_space_in_chunk.cs

@@ -104,7 +104,9 @@ public async Task a_record_is_not_written_at_first_but_written_on_second_try()
 		await using var filestream = File.Open(filename2,
 			new FileStreamOptions
 			{
-				Mode = FileMode.Open, Access = FileAccess.Read, Options = FileOptions.Asynchronous
+				Mode = FileMode.Open,
+				Access = FileAccess.Read,
+				Options = FileOptions.Asynchronous
 			});
 		filestream.Seek(ChunkHeader.Size + sizeof(int), SeekOrigin.Begin);
 		var recordLength = filestream.Length - filestream.Position;

src/EventStore.Core.Tests/TransactionLog/with_tfchunk_enumerator.cs

@@ -38,8 +38,10 @@ public async Task iterates_chunks_with_correct_callback_order()
 		var strategy = new VersionedPatternFileNamingStrategy(PathName, "chunk-");
 		var chunkEnumerator = new TFChunkEnumerator(strategy);
 		var result = new List<string>();
-		ValueTask<int> GetNextFileNumber(string chunk, int chunkNumber, int chunkVersion, CancellationToken token) {
-			return Path.GetFileName(chunk) switch {
+		ValueTask<int> GetNextFileNumber(string chunk, int chunkNumber, int chunkVersion, CancellationToken token)
+		{
+			return Path.GetFileName(chunk) switch
+			{
 				"chunk-000001.000000" => new(2),
 				"chunk-000002.000001" => new(3),
 				"chunk-000005.000000" => new(6),

src/EventStore.Core.Tests/Transforms/BitFlip/BitFlipChunkWriteTransform.cs

@@ -34,7 +34,8 @@ public async ValueTask<int> WriteFooter(ReadOnlyMemory<byte> footer, Cancellatio
 
 	private static int GetAlignedSize(int size, int alignmentSize)
 	{
-		if (size % alignmentSize == 0) return size;
+		if (size % alignmentSize == 0)
+			return size;
 		return (size / alignmentSize + 1) * alignmentSize;
 	}
 }

src/EventStore.Core.Tests/Transforms/ByteDup/ByteDupChunkReadTransform.cs

@@ -1,6 +1,7 @@
 using EventStore.Plugins.Transforms;
 
 namespace EventStore.Core.Tests.Transforms.ByteDup;
+
 public class ByteDupChunkReadTransform : IChunkReadTransform
 {
 	public ChunkDataReadStream TransformData(ChunkDataReadStream dataStream) =>

src/EventStore.Core.Tests/Transforms/ByteDup/ByteDupChunkTransform.cs

@@ -1,6 +1,7 @@
 using EventStore.Plugins.Transforms;
 
 namespace EventStore.Core.Tests.Transforms.ByteDup;
+
 public class ByteDupChunkTransform : IChunkTransform
 {
 	public IChunkReadTransform Read { get; } = new ByteDupChunkReadTransform();

src/EventStore.Core.Tests/Transforms/ByteDup/ByteDupChunkWriteTransform.cs

@@ -37,7 +37,8 @@ public async ValueTask<int> WriteFooter(ReadOnlyMemory<byte> footer, Cancellatio
 
 	private static int GetAlignedSize(int size, int alignmentSize)
 	{
-		if (size % alignmentSize == 0) return size;
+		if (size % alignmentSize == 0)
+			return size;
 		return (size / alignmentSize + 1) * alignmentSize;
 	}
 }

src/EventStore.Core.Tests/Transforms/ByteDup/ByteDupDbTransform.cs

@@ -1,6 +1,7 @@
 using EventStore.Plugins.Transforms;
 
 namespace EventStore.Core.Tests.Transforms.ByteDup;
+
 public class ByteDupDbTransform : IDbTransform
 {
 	public string Name => "bytedup";

src/EventStore.Core.Tests/Transforms/WithHeader/WithHeaderChunkReadTransform.cs

@@ -1,6 +1,7 @@
 using EventStore.Plugins.Transforms;
 
 namespace EventStore.Core.Tests.Transforms.WithHeader;
+
 public class WithHeaderChunkReadTransform(int transformHeaderSize) : IChunkReadTransform
 {
 	public ChunkDataReadStream TransformData(ChunkDataReadStream dataStream) =>

src/EventStore.Core.Tests/Transforms/WithHeader/WithHeaderChunkWriteTransform.cs

@@ -36,7 +36,8 @@ public async ValueTask<int> WriteFooter(ReadOnlyMemory<byte> footer, Cancellatio
 
 	private static int GetAlignedSize(int size, int alignmentSize)
 	{
-		if (size % alignmentSize == 0) return size;
+		if (size % alignmentSize == 0)
+			return size;
 		return (size / alignmentSize + 1) * alignmentSize;
 	}
 }

src/EventStore.Core.Tests/Transforms/WithHeader/WithHeaderDbTransform.cs

@@ -1,6 +1,7 @@
 using EventStore.Plugins.Transforms;
 
 namespace EventStore.Core.Tests.Transforms.WithHeader;
+
 public class WithHeaderDbTransform : IDbTransform
 {
 	public string Name => "withheader";