feat: prepare simulating other file systems (#546)

* Allow simulating other file systems

* Simulate `Path.IsPathRooted`

* Fix or skip failing tests

Source/Testably.Abstractions.Testing/FileSystem/DriveInfoFactoryMock.cs

@@ -30,6 +30,7 @@ public IDriveInfo[] GetDrives()
 		return _fileSystem.Storage.GetDrives()
 			.Where(x => !x.IsUncPath)
 			.Cast<IDriveInfo>()
+			.OrderBy(x => x.Name)
 			.ToArray();
 	}
 

Source/Testably.Abstractions.Testing/Helpers/Execute.LinuxPath.cs

@@ -0,0 +1,22 @@
+using System.IO;
+#if FEATURE_SPAN
+using System;
+#endif
+
+namespace Testably.Abstractions.Testing.Helpers;
+
+internal partial class Execute
+{
+	private class LinuxPath(MockFileSystem fileSystem) : NativePath(fileSystem)
+	{
+#if FEATURE_SPAN
+		/// <inheritdoc cref="Path.IsPathRooted(ReadOnlySpan{char})" />
+		public override bool IsPathRooted(ReadOnlySpan<char> path)
+			=> IsPathRooted(path.ToString());
+#endif
+
+		/// <inheritdoc cref="Path.IsPathRooted(string)" />
+		public override bool IsPathRooted(string? path)
+			=> path?.Length > 0 && path[0] == '/';
+	}
+}

Source/Testably.Abstractions.Testing/Helpers/Execute.MacPath.cs

@@ -0,0 +1,12 @@
+#if FEATURE_SPAN
+#endif
+#if FEATURE_FILESYSTEM_NET7
+using Testably.Abstractions.Testing.Storage;
+#endif
+
+namespace Testably.Abstractions.Testing.Helpers;
+
+internal partial class Execute
+{
+	private sealed class MacPath(MockFileSystem fileSystem) : LinuxPath(fileSystem);
+}

Source/Testably.Abstractions.Testing/Helpers/Execute.NativePath.cs

@@ -11,15 +11,8 @@ namespace Testably.Abstractions.Testing.Helpers;
 
 internal partial class Execute
 {
-	private sealed class NativePath : IPath
+	private class NativePath(MockFileSystem fileSystem) : IPath
 	{
-		private readonly MockFileSystem _fileSystem;
-
-		public NativePath(MockFileSystem fileSystem)
-		{
-			_fileSystem = fileSystem;
-		}
-
 		#region IPath Members
 
 		/// <inheritdoc cref="Path.AltDirectorySeparatorChar" />
@@ -31,7 +24,7 @@ public char DirectorySeparatorChar
 			=> System.IO.Path.DirectorySeparatorChar;
 
 		/// <inheritdoc cref="IFileSystemEntity.FileSystem" />
-		public IFileSystem FileSystem => _fileSystem;
+		public IFileSystem FileSystem => fileSystem;
 
 		/// <inheritdoc cref="Path.PathSeparator" />
 		public char PathSeparator
@@ -83,7 +76,7 @@ public bool Exists([NotNullWhen(true)] string? path)
 				return false;
 			}
 
-			return _fileSystem.Storage.GetContainer(_fileSystem.Storage.GetLocation(path))
+			return fileSystem.Storage.GetContainer(fileSystem.Storage.GetLocation(path))
 				is not NullContainer;
 		}
 #endif
@@ -134,11 +127,11 @@ public ReadOnlySpan<char> GetFileNameWithoutExtension(ReadOnlySpan<char> path)
 		/// <inheritdoc cref="Path.GetFullPath(string)" />
 		public string GetFullPath(string path)
 		{
-			path.EnsureValidArgument(_fileSystem, nameof(path));
+			path.EnsureValidArgument(fileSystem, nameof(path));
 
 			string? pathRoot = System.IO.Path.GetPathRoot(path);
 			string? directoryRoot =
-				System.IO.Path.GetPathRoot(_fileSystem.Storage.CurrentDirectory);
+				System.IO.Path.GetPathRoot(fileSystem.Storage.CurrentDirectory);
 			if (!string.IsNullOrEmpty(pathRoot) && !string.IsNullOrEmpty(directoryRoot))
 			{
 				if (char.ToUpperInvariant(pathRoot[0]) != char.ToUpperInvariant(directoryRoot[0]))
@@ -153,7 +146,7 @@ public string GetFullPath(string path)
 			}
 
 			return System.IO.Path.GetFullPath(System.IO.Path.Combine(
-				_fileSystem.Storage.CurrentDirectory,
+				fileSystem.Storage.CurrentDirectory,
 				path));
 		}
 
@@ -189,11 +182,11 @@ public string GetRandomFileName()
 		/// <inheritdoc cref="Path.GetRelativePath(string, string)" />
 		public string GetRelativePath(string relativeTo, string path)
 		{
-			relativeTo.EnsureValidArgument(_fileSystem, nameof(relativeTo));
-			path.EnsureValidArgument(_fileSystem, nameof(path));
+			relativeTo.EnsureValidArgument(fileSystem, nameof(relativeTo));
+			path.EnsureValidArgument(fileSystem, nameof(path));
 
-			relativeTo = _fileSystem.Execute.Path.GetFullPath(relativeTo);
-			path = _fileSystem.Execute.Path.GetFullPath(path);
+			relativeTo = fileSystem.Execute.Path.GetFullPath(relativeTo);
+			path = fileSystem.Execute.Path.GetFullPath(path);
 
 			return System.IO.Path.GetRelativePath(relativeTo, path);
 		}
@@ -235,12 +228,12 @@ public bool IsPathFullyQualified(string path)
 
 #if FEATURE_SPAN
 		/// <inheritdoc cref="Path.IsPathRooted(ReadOnlySpan{char})" />
-		public bool IsPathRooted(ReadOnlySpan<char> path)
+		public virtual bool IsPathRooted(ReadOnlySpan<char> path)
 			=> System.IO.Path.IsPathRooted(path);
 #endif
 
 		/// <inheritdoc cref="Path.IsPathRooted(string)" />
-		public bool IsPathRooted(string? path)
+		public virtual bool IsPathRooted(string? path)
 			=> System.IO.Path.IsPathRooted(path);
 
 #if FEATURE_PATH_JOIN

Source/Testably.Abstractions.Testing/Helpers/Execute.WindowsPath.cs

@@ -0,0 +1,40 @@
+using System.IO;
+#if FEATURE_SPAN
+using System;
+#endif
+
+namespace Testably.Abstractions.Testing.Helpers;
+
+internal partial class Execute
+{
+	private sealed class WindowsPath(MockFileSystem fileSystem) : NativePath(fileSystem)
+	{
+#if FEATURE_SPAN
+		/// <inheritdoc cref="Path.IsPathRooted(ReadOnlySpan{char})" />
+		public override bool IsPathRooted(ReadOnlySpan<char> path)
+			=> IsPathRooted(path.ToString());
+#endif
+
+		/// <inheritdoc cref="Path.IsPathRooted(string)" />
+		public override bool IsPathRooted(string? path)
+		{
+			int? length = path?.Length;
+			return (length >= 1 && IsDirectorySeparator(path![0])) ||
+			       (length >= 2 && IsValidDriveChar(path![0]) && path[1] == VolumeSeparatorChar);
+		}
+
+		/// <summary>
+		///     True if the given character is a directory separator.
+		/// </summary>
+		/// <remarks>https://github.com/dotnet/runtime/blob/v8.0.3/src/libraries/Common/src/System/IO/PathInternal.Windows.cs#L280</remarks>
+		private static bool IsDirectorySeparator(char c)
+			=> c == '\\' || c == '/';
+
+		/// <summary>
+		///     Returns true if the given character is a valid drive letter
+		/// </summary>
+		/// <remarks>https://github.com/dotnet/runtime/blob/v8.0.3/src/libraries/Common/src/System/IO/PathInternal.Windows.cs#L72</remarks>
+		private static bool IsValidDriveChar(char value)
+			=> (uint)((value | 0x20) - 'a') <= 'z' - 'a';
+	}
+}

Source/Testably.Abstractions.Testing/Helpers/Execute.cs

@@ -47,7 +47,23 @@ internal Execute(MockFileSystem fileSystem, OSPlatform osPlatform, bool isNetFra
 		StringComparisonMode = IsLinux
 			? StringComparison.Ordinal
 			: StringComparison.OrdinalIgnoreCase;
-		Path = new NativePath(fileSystem);
+		if (IsLinux)
+		{
+			Path = new LinuxPath(fileSystem);
+		}
+		else if (IsMac)
+		{
+			Path = new MacPath(fileSystem);
+		}
+		else if (IsWindows)
+		{
+			Path = new WindowsPath(fileSystem);
+		}
+		else
+		{
+			throw new NotSupportedException(
+				"The operating system must be one of Linux, OSX or Windows");
+		}
 	}
 
 	internal Execute(MockFileSystem fileSystem)

Source/Testably.Abstractions.Testing/MockFileSystem.cs

@@ -2,6 +2,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.Runtime.InteropServices;
 using Testably.Abstractions.Testing.FileSystem;
 using Testably.Abstractions.Testing.Helpers;
 using Testably.Abstractions.Testing.Statistics;
@@ -82,9 +83,19 @@ internal IReadOnlyList<IStorageContainer> StorageContainers
 	/// <summary>
 	///     Initializes the <see cref="MockFileSystem" />.
 	/// </summary>
-	public MockFileSystem()
+	public MockFileSystem() : this(_ => { }) { }
+
+	/// <summary>
+	///     Initializes the <see cref="MockFileSystem" /> with the <paramref name="initializationCallback" />.
+	/// </summary>
+	internal MockFileSystem(Action<Initialization> initializationCallback)
 	{
-		Execute = new Execute(this);
+		Initialization initialization = new();
+		initializationCallback(initialization);
+
+		Execute = initialization.OperatingSystem == null
+			? new Execute(this)
+			: new Execute(this, initialization.OperatingSystem.Value);
 		StatisticsRegistration = new FileSystemStatistics(this);
 		using IDisposable release = StatisticsRegistration.Ignore();
 		RandomSystem = new MockRandomSystem();
@@ -101,7 +112,7 @@ public MockFileSystem()
 		FileSystemWatcher = new FileSystemWatcherFactoryMock(this);
 		SafeFileHandleStrategy = new NullSafeFileHandleStrategy();
 		AccessControlStrategy = new NullAccessControlStrategy();
-		AddDriveFromCurrentDirectory();
+		InitializeFileSystem(initialization);
 	}
 
 	#region IFileSystem Members
@@ -181,11 +192,17 @@ public MockFileSystem WithSafeFileHandleStrategy(
 		return this;
 	}
 
-	private void AddDriveFromCurrentDirectory()
+	private void InitializeFileSystem(Initialization initialization)
 	{
 		try
 		{
-			string? root = Path.GetPathRoot(System.IO.Directory.GetCurrentDirectory());
+			if (initialization.CurrentDirectory != null)
+			{
+				IDirectoryInfo directoryInfo = DirectoryInfo.New(initialization.CurrentDirectory);
+				Storage.CurrentDirectory = directoryInfo.FullName;
+			}
+
+			string? root = Execute.Path.GetPathRoot(Directory.GetCurrentDirectory());
 			if (root != null &&
 			    root[0] != _storage.MainDrive.Name[0])
 			{
@@ -198,4 +215,61 @@ private void AddDriveFromCurrentDirectory()
 			// due to brittle tests on MacOS
 		}
 	}
+
+	/// <summary>
+	///     The initialization options for the <see cref="MockFileSystem" />.
+	/// </summary>
+	internal class Initialization
+	{
+		/// <summary>
+		///     The current directory.
+		/// </summary>
+		internal string? CurrentDirectory { get; private set; }
+
+		/// <summary>
+		///     The simulated operating system.
+		/// </summary>
+		internal OSPlatform? OperatingSystem { get; private set; }
+
+		/// <summary>
+		///     Specify the operating system that should be simulated.
+		/// </summary>
+		/// <remarks>
+		///     Supported values are<br />
+		///     - <see cref="OSPlatform.Linux" /><br />
+		///     - <see cref="OSPlatform.OSX" /><br />
+		///     - <see cref="OSPlatform.Windows" />
+		/// </remarks>
+		internal Initialization SimulatingOperatingSystem(OSPlatform operatingSystem)
+		{
+			if (operatingSystem != OSPlatform.Linux &&
+			    operatingSystem != OSPlatform.OSX &&
+			    operatingSystem != OSPlatform.Windows)
+			{
+				throw new NotSupportedException(
+					"Only Linux, OSX and Windows are supported operating systems.");
+			}
+
+			OperatingSystem = operatingSystem;
+			return this;
+		}
+
+		/// <summary>
+		///     Use the provided <paramref name="path" /> as current directory.
+		/// </summary>
+		internal Initialization UseCurrentDirectory(string path)
+		{
+			CurrentDirectory = path;
+			return this;
+		}
+
+		/// <summary>
+		///     Use <see cref="Directory.GetCurrentDirectory()" /> as current directory.
+		/// </summary>
+		internal Initialization UseCurrentDirectory()
+		{
+			CurrentDirectory = System.IO.Directory.GetCurrentDirectory();
+			return this;
+		}
+	}
 }

Tests/Testably.Abstractions.Testing.Tests/Helpers/ExecuteTests.cs

@@ -5,6 +5,23 @@ namespace Testably.Abstractions.Testing.Tests.Helpers;
 
 public sealed class ExecuteTests
 {
+#if !NET48
+	[Fact]
+	public void Constructor_ForFreeBSD_ShouldThrowNotSupportedException()
+	{
+		Exception? exception = Record.Exception(() =>
+		{
+			_ = new Execute(new MockFileSystem(), OSPlatform.FreeBSD);
+		});
+
+		exception.Should().BeOfType<NotSupportedException>()
+			.Which.Message.Should()
+			.Contain("Linux").And
+			.Contain("Windows").And
+			.Contain("OSX");
+	}
+#endif
+
 	[Fact]
 	public void Constructor_ForLinux_ShouldInitializeAccordingly()
 	{