The Cocoar.FileSystem library has comprehensive test coverage across all major components and platforms (Windows, Linux, macOS).

Total Tests: 98

• ResilientFileSystemMonitor: 28 tests
• FileSearcher: 20 tests
• FileReader: 18 tests
• FluentApi: 32 tests

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• Constructor_WithNullOptions_ShouldThrow
• Constructor_WithNullPath_ShouldThrow
• Constructor_WithEmptyPath_ShouldThrow
• Constructor_WithWhitespacePath_ShouldThrow
• Constructor_WithValidOptions_ShouldNotThrow

• FileCreation_ShouldTriggerCreatedEvent - Tests file creation detection
• FileChange_ShouldTriggerChangedEvent - Tests file modification detection
• FileDelete_ShouldTriggerDeletedEvent - Tests file deletion detection
• FileRenamed_ShouldTriggerRenamedEvent - Tests file rename detection

• Filter_OnlyMatchingFiles_ShouldTriggerEvents - Tests file pattern filtering (*.txt, etc.)
• IncludeSubdirectories_True_ShouldMonitorSubfolders - Tests recursive monitoring
• IncludeSubdirectories_False_ShouldNotMonitorSubfolders - Tests non-recursive monitoring

• RapidFileChanges_WithoutDebouncing_ShouldReceiveAllEvents - Tests lossless event delivery
• RapidFileChanges_WithDebouncing_ShouldLimitEvents - Tests debouncing reduces event flood

• DirectoryDeleted_AndRecreatedWithFiles_ShouldDetectAllFiles - Tests recovery with file reconciliation
• DirectoryDeleted_AndRecreatedWithDifferentFiles_ShouldReconcile - Tests differential reconciliation
• FileModified_WhileInPollingMode_ShouldDetectChange - Tests change detection during polling

• HealthCheck_DirectoryDisappears_ShouldTransitionToPolling - Tests directory deletion detection via health check
• AuditInterval_DetectsSilentChanges_ShouldReconcile - Tests metadata fingerprint auditing

• PollingMode_ShouldDetectFileChanges - Tests polling fallback when directory doesn't exist
• PollingMode_DirectoryAppearsLater_ShouldSwitchToWatcher - Tests automatic recovery to watcher mode

• ModeChanged_Event_ShouldProvideReasonAndMode - Tests mode transition notifications

• Constructor_WithExistingPath_ShouldStartWatcher - Tests proper initialization
• Dispose_ShouldCleanupResources - Tests proper cleanup
• Dispose_MultipleTimes_ShouldNotThrow - Tests idempotent disposal

• MultipleFiles_RapidCreation_ShouldDetectAll - Tests handling 20+ files created rapidly
• Constructor_WithNonExistentPath_AndPollingEnabled_ShouldStartPolling - Tests startup in polling mode

• Events_ChannelReader_ShouldReceiveAllEventsInOrder - Tests ChannelReader API

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• EnumerateFiles_WithNullSearchPath_ShouldThrow
• EnumerateFiles_WithNullSearchPattern_ShouldThrow
• EnumerateFiles_WithEmptySearchPattern_ShouldThrow
• EnumerateFiles_WithWhitespaceSearchPattern_ShouldThrow
• EnumerateFiles_WithNonExistentDirectory_ShouldThrow

• EnumerateFiles_WithEmptyDirectory_ShouldReturnEmpty
• EnumerateFiles_WithSingleFile_ShouldReturnThatFile
• EnumerateFiles_WithMultipleFiles_ShouldReturnAll
• EnumerateFiles_WithWildcardPattern_ShouldReturnAllFiles
• EnumerateFiles_WithComplexPattern_ShouldMatchCorrectly

• EnumerateFiles_WithSubdirectories_NoMaxDepth_ShouldRecurseAll
• EnumerateFiles_WithMaxDepth_Zero_ShouldReturnOnlyRootFiles
• EnumerateFiles_WithMaxDepth_One_ShouldReturnRootAndFirstLevel

• EnumerateFiles_WithExcludedFolders_ShouldSkipThem
• EnumerateFiles_WithNestedExcludedFolders_ShouldSkipEntireTree
• EnumerateFiles_WithNullExcludedFolders_ShouldIncludeAll
• EnumerateFiles_WithMultipleExcludedFolders_ShouldSkipAll

• EnumerateFiles_WithDeepNesting_ShouldHandleEfficiently - Tests 10 levels deep
• EnumerateFiles_WithManyFiles_ShouldHandleEfficiently - Tests 100 files
• EnumerateFiles_IsLazyEvaluated_ShouldNotEnumerateAll - Tests deferred execution

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All tests run on:

• ✅ Windows (latest)
• ✅ Linux (ubuntu-latest)
• ✅ macOS (latest)

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Indirectly tested through:

• Directory delete/recreate scenarios
• Health check transitions
• Automatic recovery tests

Platform-specific identity (Windows: FileId, Unix: inode) is verified through cross-platform CI.

• Reconciliation after directory recreation
• Events delivered in order via Channel
• No dropped events during mode transitions

• macOS directory replacement detection
• Health check on all platforms
• Polling fallback consistency

• Lazy file enumeration
• Efficient directory traversal
• Minimal overhead for health checks

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• ReadAllBytes_WithValidFile_ShouldReturnContent - Tests basic file reading
• ReadAllBytes_WithEmptyFile_ShouldReturnEmptyArray - Tests empty file handling
• ReadAllBytes_WithLargeFile_ShouldReadCompletely - Tests 1 MB file reading

• ReadAllBytes_WithUtf8Bom_AndStripEnabled_ShouldRemoveBom - Tests BOM removal
• ReadAllBytes_WithUtf8Bom_AndStripDisabled_ShouldKeepBom - Tests BOM preservation
• ReadAllBytes_WithoutBom_AndStripEnabled_ShouldReturnAsIs - Tests file without BOM
• ReadAllBytes_WithPartialBom_ShouldNotStrip - Tests incomplete BOM (only 2 bytes)
• ReadAllBytes_WithOnlyBom_AndStripEnabled_ShouldReturnEmpty - Tests file with only BOM
• TryReadAllBytes_WithUtf8Bom_AndStripEnabled_ShouldRemoveBom - Tests BOM removal in Try variant

• ReadAllBytes_WithSharedAccess_ShouldAllowReading - Tests FileShare.ReadWrite behavior

• ReadAllBytes_WithNullPath_ShouldThrow - Tests ArgumentNullException
• ReadAllBytes_WithEmptyPath_ShouldThrow - Tests ArgumentException
• ReadAllBytes_WithWhitespacePath_ShouldThrow - Tests ArgumentException
• ReadAllBytes_WithNonExistentFile_ShouldThrow - Tests FileNotFoundException

• TryReadAllBytes_WithValidFile_ShouldReturnContent - Tests successful read
• TryReadAllBytes_WithNonExistentFile_ShouldReturnNull - Tests null return for missing file
• TryReadAllBytes_WithNullPath_ShouldThrow - Tests validation
• TryReadAllBytes_WithEmptyPath_ShouldThrow - Tests validation
• TryReadAllBytes_WithWhitespacePath_ShouldThrow - Tests validation

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All tests run on:

• ✅ Windows (latest)
• ✅ Linux (ubuntu-latest)
• ✅ macOS (latest)

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Indirectly tested through:

• Directory delete/recreate scenarios
• Health check transitions
• Automatic recovery tests

Platform-specific identity (Windows: FileId, Unix: inode) is verified through cross-platform CI.

• Reconciliation after directory recreation
• Event ordering via Channel serialization
• No missed events during rapid file creation

• Survives directory deletion
• Auto-recovery when directory reappears
• Graceful fallback to polling
• Health check detection of "zombie" watchers

• Debouncing to reduce event floods
• Efficient metadata fingerprint auditing
• Fast file enumeration with depth/exclusion control

• Traditional .NET events (Created, Changed, Deleted, Renamed, Error, ModeChanged)
• Modern unified stream via ChannelReader<FileSystemEvent>
• Multiple concurrent consumers supported

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Custom test helpers to avoid flaky Task.Delay and improve test reliability:

• WaitUntilAsync - Polls condition until true or timeout
• WaitForConditionAsync - Alternative with custom polling interval

All file system tests use active waiting instead of fixed delays to handle platform timing differences.

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Tests account for these platform-specific behaviors:

• macOS: FileSystemWatcher can "zombie" without raising Error when directory is deleted/recreated
• Windows: FileSystemWatcher typically raises Error on directory deletion
• Linux: Behavior varies by filesystem (ext4, btrfs, etc.)

Our tests validate the resilient behavior works correctly on all platforms despite these differences.