fix: use UTF8 encoding without preamble as default

Tests/Testably.Abstractions.Tests/FileSystem/File/AppendAllLinesAsyncTests.cs

@@ -5,7 +5,6 @@
 using System.Linq;
 using System.Text;
 using System.Threading;
-using System.Threading.Tasks;
 
 namespace Testably.Abstractions.Tests.FileSystem.File;
 
@@ -43,16 +42,32 @@ await FileSystem.File.AppendAllLinesAsync(path, contents, Encoding.UTF8,
 		await That(Act).Throws<TaskCanceledException>().WithHResult(-2146233029);
 	}
 
+	[Theory]
+	[AutoData]
+	public async Task AppendAllLinesAsync_Enumerable_WithoutEncoding_ShouldUseUtf8(
+		string path)
+	{
+		string[] contents = ["breuß"];
+
+		await FileSystem.File.AppendAllLinesAsync(path, contents.AsEnumerable(),
+			CancellationToken.None);
+
+		byte[] bytes = FileSystem.File.ReadAllBytes(path);
+		await That(bytes.Length).IsEqualTo(6 + Environment.NewLine.Length);
+	}
+
 	[Theory]
 	[AutoData]
 	public async Task AppendAllLinesAsync_ExistingFile_ShouldAppendLinesToFile(
 		string path, List<string> previousContents, List<string> contents)
 	{
 		string expectedContent = string.Join(Environment.NewLine, previousContents.Concat(contents))
 		                         + Environment.NewLine;
-		await FileSystem.File.AppendAllLinesAsync(path, previousContents, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllLinesAsync(path, previousContents,
+			TestContext.Current.CancellationToken);
 
-		await FileSystem.File.AppendAllLinesAsync(path, contents, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllLinesAsync(path, contents,
+			TestContext.Current.CancellationToken);
 
 		await That(FileSystem.File.Exists(path)).IsTrue();
 		await That(FileSystem.File.ReadAllText(path)).IsEqualTo(expectedContent);
@@ -67,7 +82,8 @@ public async Task AppendAllLinesAsync_MissingDirectory_ShouldThrowDirectoryNotFo
 
 		async Task Act()
 		{
-			await FileSystem.File.AppendAllLinesAsync(filePath, contents, TestContext.Current.CancellationToken);
+			await FileSystem.File.AppendAllLinesAsync(filePath, contents,
+				TestContext.Current.CancellationToken);
 		}
 
 		await That(Act).Throws<DirectoryNotFoundException>().WithHResult(-2147024893);
@@ -81,7 +97,8 @@ public async Task AppendAllLinesAsync_MissingFile_ShouldCreateFile(
 		string expectedContent = string.Join(Environment.NewLine, contents)
 		                         + Environment.NewLine;
 
-		await FileSystem.File.AppendAllLinesAsync(path, contents, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllLinesAsync(path, contents,
+			TestContext.Current.CancellationToken);
 
 		await That(FileSystem.File.Exists(path)).IsTrue();
 		await That(FileSystem.File.ReadAllText(path)).IsEqualTo(expectedContent);
@@ -94,7 +111,8 @@ public async Task AppendAllLinesAsync_NullContent_ShouldThrowArgumentNullExcepti
 	{
 		async Task Act()
 		{
-			await FileSystem.File.AppendAllLinesAsync(path, null!, TestContext.Current.CancellationToken);
+			await FileSystem.File.AppendAllLinesAsync(path, null!,
+				TestContext.Current.CancellationToken);
 		}
 
 		await That(Act).Throws<ArgumentNullException>()
@@ -109,7 +127,8 @@ public async Task AppendAllLinesAsync_NullEncoding_ShouldThrowArgumentNullExcept
 	{
 		async Task Act()
 		{
-			await FileSystem.File.AppendAllLinesAsync(path, [], null!, TestContext.Current.CancellationToken);
+			await FileSystem.File.AppendAllLinesAsync(path, [], null!,
+				TestContext.Current.CancellationToken);
 		}
 
 		await That(Act).Throws<ArgumentNullException>()
@@ -124,7 +143,8 @@ public async Task AppendAllLinesAsync_ShouldEndWithNewline(string path)
 		string[] contents = ["foo", "bar"];
 		string expectedResult = "foo" + Environment.NewLine + "bar" + Environment.NewLine;
 
-		await FileSystem.File.AppendAllLinesAsync(path, contents, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllLinesAsync(path, contents,
+			TestContext.Current.CancellationToken);
 
 		await That(FileSystem.File.Exists(path)).IsTrue();
 		await That(FileSystem.File.ReadAllText(path)).IsEqualTo(expectedResult);
@@ -140,7 +160,8 @@ public async Task
 
 		async Task Act()
 		{
-			await FileSystem.File.AppendAllLinesAsync(path, contents, TestContext.Current.CancellationToken);
+			await FileSystem.File.AppendAllLinesAsync(path, contents,
+				TestContext.Current.CancellationToken);
 		}
 
 		await That(Act).Throws<UnauthorizedAccessException>().WithHResult(-2147024891);
@@ -157,7 +178,8 @@ public async Task
 		string path = new Fixture().Create<string>();
 		string[] lines = new Fixture().Create<string[]>();
 		lines[1] = specialLine;
-		await FileSystem.File.AppendAllLinesAsync(path, lines, writeEncoding, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllLinesAsync(path, lines, writeEncoding,
+			TestContext.Current.CancellationToken);
 
 		string[] result = FileSystem.File.ReadAllLines(path, readEncoding);
 

Tests/Testably.Abstractions.Tests/FileSystem/File/AppendAllLinesTests.cs

@@ -8,6 +8,19 @@ namespace Testably.Abstractions.Tests.FileSystem.File;
 [FileSystemTests]
 public partial class AppendAllLinesTests
 {
+	[Theory]
+	[AutoData]
+	public async Task AppendAllLines_Enumerable_WithoutEncoding_ShouldUseUtf8(
+		string path)
+	{
+		string[] contents = ["breuß"];
+
+		FileSystem.File.AppendAllLines(path, contents.AsEnumerable());
+
+		byte[] bytes = FileSystem.File.ReadAllBytes(path);
+		await That(bytes.Length).IsEqualTo(6 + Environment.NewLine.Length);
+	}
+
 	[Theory]
 	[AutoData]
 	public async Task AppendAllLines_ExistingFile_ShouldAppendLinesToFile(
@@ -112,4 +125,17 @@ public async Task AppendAllLines_WithDifferentEncoding_ShouldNotReturnWrittenTex
 		await That(result).IsNotEqualTo(lines).InAnyOrder();
 		await That(result[0]).IsEqualTo(lines[0]);
 	}
+
+	[Theory]
+	[AutoData]
+	public async Task AppendAllLines_WithoutEncoding_ShouldUseUtf8(
+		string path)
+	{
+		string[] contents = ["breuß"];
+
+		FileSystem.File.AppendAllLines(path, contents);
+
+		byte[] bytes = FileSystem.File.ReadAllBytes(path);
+		await That(bytes.Length).IsEqualTo(6 + Environment.NewLine.Length);
+	}
 }

Tests/Testably.Abstractions.Tests/FileSystem/File/AppendAllTextAsyncTests.cs

@@ -44,9 +44,11 @@ async Task Act() =>
 	public async Task AppendAllTextAsync_ExistingFile_ShouldAppendLinesToFile(
 		string path, string previousContents, string contents)
 	{
-		await FileSystem.File.AppendAllTextAsync(path, previousContents, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllTextAsync(path, previousContents,
+			TestContext.Current.CancellationToken);
 
-		await FileSystem.File.AppendAllTextAsync(path, contents, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllTextAsync(path, contents,
+			TestContext.Current.CancellationToken);
 
 		await That(FileSystem.File.Exists(path)).IsTrue();
 		await That(FileSystem.File.ReadAllText(path)).IsEqualTo(previousContents + contents);
@@ -61,7 +63,8 @@ public async Task AppendAllTextAsync_MissingDirectory_ShouldThrowDirectoryNotFou
 
 		async Task Act()
 		{
-			await FileSystem.File.AppendAllTextAsync(filePath, contents, TestContext.Current.CancellationToken);
+			await FileSystem.File.AppendAllTextAsync(filePath, contents,
+				TestContext.Current.CancellationToken);
 		}
 
 		await That(Act).Throws<DirectoryNotFoundException>().WithHResult(-2147024893);
@@ -72,7 +75,8 @@ async Task Act()
 	public async Task AppendAllTextAsync_MissingFile_ShouldCreateFile(
 		string path, string contents)
 	{
-		await FileSystem.File.AppendAllTextAsync(path, contents, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllTextAsync(path, contents,
+			TestContext.Current.CancellationToken);
 
 		await That(FileSystem.File.Exists(path)).IsTrue();
 		await That(FileSystem.File.ReadAllText(path)).IsEqualTo(contents);
@@ -84,7 +88,8 @@ public async Task AppendAllTextAsync_ShouldNotEndWithNewline(string path)
 	{
 		string contents = "foo";
 
-		await FileSystem.File.AppendAllTextAsync(path, contents, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllTextAsync(path, contents,
+			TestContext.Current.CancellationToken);
 
 		await That(FileSystem.File.Exists(path)).IsTrue();
 		await That(FileSystem.File.ReadAllText(path)).IsEqualTo(contents);
@@ -100,7 +105,8 @@ public async Task
 
 		async Task Act()
 		{
-			await FileSystem.File.AppendAllTextAsync(path, contents, TestContext.Current.CancellationToken);
+			await FileSystem.File.AppendAllTextAsync(path, contents,
+				TestContext.Current.CancellationToken);
 		}
 
 		await That(Act).Throws<UnauthorizedAccessException>().WithHResult(-2147024891);
@@ -114,13 +120,27 @@ public async Task AppendAllTextAsync_WithDifferentEncoding_ShouldNotReturnWritte
 		string contents, Encoding writeEncoding, Encoding readEncoding)
 	{
 		string path = new Fixture().Create<string>();
-		await FileSystem.File.AppendAllTextAsync(path, contents, writeEncoding, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllTextAsync(path, contents, writeEncoding,
+			TestContext.Current.CancellationToken);
 
 		string[] result = FileSystem.File.ReadAllLines(path, readEncoding);
 
 		await That(result).IsNotEqualTo([contents]);
 	}
 
+	[Theory]
+	[AutoData]
+	public async Task AppendAllTextAsync_WithoutEncoding_ShouldUseUtf8(
+		string path)
+	{
+		string contents = "breuß";
+
+		await FileSystem.File.AppendAllTextAsync(path, contents, CancellationToken.None);
+
+		byte[] bytes = FileSystem.File.ReadAllBytes(path);
+		await That(bytes.Length).IsEqualTo(6);
+	}
+
 #if FEATURE_FILE_SPAN
 	[Theory]
 	[AutoData]
@@ -146,7 +166,8 @@ public async Task
 		cts.Cancel();
 
 		async Task Act() =>
-			await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(), Encoding.UTF8, cts.Token);
+			await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(), Encoding.UTF8,
+				cts.Token);
 
 		await That(Act).Throws<TaskCanceledException>().WithHResult(-2146233029);
 	}
@@ -156,24 +177,28 @@ async Task Act() =>
 	public async Task AppendAllTextAsync_ReadOnlyMemory_ExistingFile_ShouldAppendLinesToFile(
 		string path, string previousContents, string contents)
 	{
-		await FileSystem.File.AppendAllTextAsync(path, previousContents, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllTextAsync(path, previousContents,
+			TestContext.Current.CancellationToken);
 
-		await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(), TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(),
+			TestContext.Current.CancellationToken);
 
 		await That(FileSystem.File.Exists(path)).IsTrue();
 		await That(FileSystem.File.ReadAllText(path)).IsEqualTo(previousContents + contents);
 	}
 
 	[Theory]
 	[AutoData]
-	public async Task AppendAllTextAsync_ReadOnlyMemory_MissingDirectory_ShouldThrowDirectoryNotFoundException(
-		string missingPath, string fileName, string contents)
+	public async Task
+		AppendAllTextAsync_ReadOnlyMemory_MissingDirectory_ShouldThrowDirectoryNotFoundException(
+			string missingPath, string fileName, string contents)
 	{
 		string filePath = FileSystem.Path.Combine(missingPath, fileName);
 
 		async Task Act()
 		{
-			await FileSystem.File.AppendAllTextAsync(filePath, contents.AsMemory(), TestContext.Current.CancellationToken);
+			await FileSystem.File.AppendAllTextAsync(filePath, contents.AsMemory(),
+				TestContext.Current.CancellationToken);
 		}
 
 		await That(Act).Throws<DirectoryNotFoundException>().WithHResult(-2147024893);
@@ -184,7 +209,8 @@ async Task Act()
 	public async Task AppendAllTextAsync_ReadOnlyMemory_MissingFile_ShouldCreateFile(
 		string path, string contents)
 	{
-		await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(), TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(),
+			TestContext.Current.CancellationToken);
 
 		await That(FileSystem.File.Exists(path)).IsTrue();
 		await That(FileSystem.File.ReadAllText(path)).IsEqualTo(contents);
@@ -196,7 +222,8 @@ public async Task AppendAllTextAsync_ReadOnlyMemory_ShouldNotEndWithNewline(stri
 	{
 		string contents = "foo";
 
-		await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(), TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(),
+			TestContext.Current.CancellationToken);
 
 		await That(FileSystem.File.Exists(path)).IsTrue();
 		await That(FileSystem.File.ReadAllText(path)).IsEqualTo(contents);
@@ -212,7 +239,8 @@ public async Task
 
 		async Task Act()
 		{
-			await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(), TestContext.Current.CancellationToken);
+			await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(),
+				TestContext.Current.CancellationToken);
 		}
 
 		await That(Act).Throws<UnauthorizedAccessException>().WithHResult(-2147024891);
@@ -222,16 +250,31 @@ async Task Act()
 
 	[Theory]
 	[ClassData(typeof(TestDataGetEncodingDifference))]
-	public async Task AppendAllTextAsync_ReadOnlyMemory_WithDifferentEncoding_ShouldNotReturnWrittenText(
-		string contents, Encoding writeEncoding, Encoding readEncoding)
+	public async Task
+		AppendAllTextAsync_ReadOnlyMemory_WithDifferentEncoding_ShouldNotReturnWrittenText(
+			string contents, Encoding writeEncoding, Encoding readEncoding)
 	{
 		string path = new Fixture().Create<string>();
-		await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(), writeEncoding, TestContext.Current.CancellationToken);
+		await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(), writeEncoding,
+			TestContext.Current.CancellationToken);
 
 		string[] result = FileSystem.File.ReadAllLines(path, readEncoding);
 
 		await That(result).IsNotEqualTo([contents]);
 	}
+
+	[Theory]
+	[AutoData]
+	public async Task AppendAllTextAsync_ReadOnlyMemory_WithoutEncoding_ShouldUseUtf8(
+		string path)
+	{
+		string contents = "breuß";
+
+		await FileSystem.File.AppendAllTextAsync(path, contents.AsMemory(), CancellationToken.None);
+
+		byte[] bytes = FileSystem.File.ReadAllBytes(path);
+		await That(bytes.Length).IsEqualTo(6);
+	}
 #endif
 }
 #endif