Fix flaky CI: default SyncOptions, pause test race, job timeout

.github/workflows/dotnet.yml

@@ -16,6 +16,8 @@ jobs:
         os: [ubuntu-latest, windows-latest, macos-latest]
 
     runs-on: ${{ matrix.os }}
+    # Fail hung test runs quickly instead of waiting for GitHub's 6-hour default
+    timeout-minutes: 30
 
     steps:
     - uses: actions/checkout@v7

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+
+- `SynchronizeAsync`, `SyncFolderAsync`, and `SyncFilesAsync` called without `SyncOptions` ignored the documented option defaults, so `PreserveTimestamps` and `PreservePermissions` were effectively off. The engine now falls back to a default `SyncOptions` instance. Besides losing timestamps, this could make a later sync treat an unchanged file as modified and raise a spurious conflict.
+
 ## [1.0.3] - 2026-07-17
 
 ### Security

src/SharpSync/Sync/SyncEngine.cs

@@ -194,7 +194,7 @@ public async Task<SyncResult> SynchronizeAsync(SyncOptions? options = null, Canc
             }
             _currentSyncCts = linkedCts;
             _currentMaxBytesPerSecond = options?.MaxBytesPerSecond;
-            _currentOptions = options;
+            _currentOptions = options ?? new SyncOptions();
             var syncToken = linkedCts.Token;
             var result = new SyncResult();
             var sw = Stopwatch.StartNew();
@@ -1722,7 +1722,7 @@ public async Task<SyncResult> SyncFolderAsync(string folderPath, SyncOptions? op
             }
             _currentSyncCts = linkedCts;
             _currentMaxBytesPerSecond = options?.MaxBytesPerSecond;
-            _currentOptions = options;
+            _currentOptions = options ?? new SyncOptions();
             var syncToken = linkedCts.Token;
             var result = new SyncResult();
             var sw = Stopwatch.StartNew();
@@ -1807,7 +1807,7 @@ public async Task<SyncResult> SyncFilesAsync(IEnumerable<string> filePaths, Sync
             }
             _currentSyncCts = linkedCts;
             _currentMaxBytesPerSecond = options?.MaxBytesPerSecond;
-            _currentOptions = options;
+            _currentOptions = options ?? new SyncOptions();
             var syncToken = linkedCts.Token;
             var result = new SyncResult();
             var sw = Stopwatch.StartNew();

tests/SharpSync.Tests/Sync/SyncEngineOptionsTests.cs

@@ -527,6 +527,22 @@ public async Task SynchronizeAsync_PreserveTimestampsFalse_DoesNotPreserve() {
         Assert.True((DateTime.UtcNow - remoteTimestamp).TotalSeconds < 30);
     }
 
+    [Fact]
+    public async Task SynchronizeAsync_NoOptions_PreservesTimestampsByDefault() {
+        // Arrange
+        var specificTime = new DateTime(2024, 3, 10, 8, 0, 0, DateTimeKind.Utc);
+        await File.WriteAllTextAsync(Path.Combine(_localDir, "default_ts.txt"), "default timestamp");
+        File.SetLastWriteTimeUtc(Path.Combine(_localDir, "default_ts.txt"), specificTime);
+
+        // Act - no options passed, so SyncOptions defaults (PreserveTimestamps = true) must apply
+        var result = await _syncEngine.SynchronizeAsync();
+
+        Assert.True(result.Success);
+
+        var remoteTimestamp = File.GetLastWriteTimeUtc(Path.Combine(_remoteDir, "default_ts.txt"));
+        Assert.Equal(specificTime, remoteTimestamp, TimeSpan.FromSeconds(2));
+    }
+
     #endregion
 
     #region PreservePermissions with Mocks

tests/SharpSync.Tests/Sync/SyncEngineTests.cs

@@ -1099,32 +1099,39 @@ public async Task PauseAsync_CalledMultipleTimes_IsIdempotent() {
             await File.WriteAllTextAsync(filePath, "content");
         }
 
-        var pauseSignal = new TaskCompletionSource();
+        var pauseRequested = 0;
+        var pauseCalls = new TaskCompletionSource<Task[]>(TaskCreationOptions.RunContinuationsAsynchronously);
 
         _syncEngine.ProgressChanged += (sender, args) => {
-            if (args.Operation != SyncOperation.Scanning && !pauseSignal.Task.IsCompleted) {
-                // Call pause multiple times
-                _ = Task.Run(async () => {
-                    await _syncEngine.PauseAsync();
-                    await _syncEngine.PauseAsync();
-                    await _syncEngine.PauseAsync();
-                    pauseSignal.TrySetResult();
-                });
+            // Pause once, from the first non-scanning event only. All three calls happen here,
+            // before the test resumes, so no late pause can leave the engine paused forever.
+            if (args.Operation != SyncOperation.Scanning && Interlocked.Exchange(ref pauseRequested, 1) == 0) {
+                pauseCalls.TrySetResult([_syncEngine.PauseAsync(), _syncEngine.PauseAsync(), _syncEngine.PauseAsync()]);
             }
         };
 
         // Act
         var syncTask = Task.Run(() => _syncEngine.SynchronizeAsync());
 
-        await Task.WhenAny(pauseSignal.Task, Task.Delay(TimeSpan.FromSeconds(2)));
+        if (await Task.WhenAny(pauseCalls.Task, syncTask) == pauseCalls.Task) {
+            var calls = await pauseCalls.Task;
+
+            // Repeated calls while already paused are no-ops and complete immediately
+            Assert.True(calls[1].IsCompleted);
+            Assert.True(calls[2].IsCompleted);
+
+            // Wait for a pause point, or for sync to finish if the pause came after the last one
+            await Task.WhenAny(calls[0], syncTask);
+        }
 
         // Resume to complete
         await _syncEngine.ResumeAsync();
 
-        var result = await syncTask;
+        var result = await syncTask.WaitAsync(TimeSpan.FromSeconds(30));
 
         // Assert - Should complete without errors
         Assert.True(result.Success);
+        Assert.Equal(SyncEngineState.Idle, _syncEngine.State);
     }
 
     [Fact]