fix: use UTF8 encoding without preamble as default

[vbreuss]

This PR fixes the default encoding behavior in file write and append methods to use UTF-8 without BOM (byte order mark) instead of the system default encoding when no encoding is explicitly specified. This improves cross-platform compatibility.

Key Changes:

• Modified file write/append methods to use UTF-8 encoding without preamble as default
• Consolidated encoding logic into a single WriteText helper method
• Added comprehensive tests to verify UTF-8 encoding behavior across all affected methods

---

• Fixes Bug: FileMock.WriteAllLines use system encoding instead of UTF8 without BOM #843

[Copilot]

Pull Request Overview

This PR fixes the default encoding behavior in file write and append methods to use UTF-8 without BOM (byte order mark) instead of the system default encoding when no encoding is explicitly specified. This addresses issue #843 and improves cross-platform compatibility.

Key Changes:

• Modified file write/append methods to use UTF-8 encoding without preamble as default
• Consolidated encoding logic into a single WriteText helper method
• Added comprehensive tests to verify UTF-8 encoding behavior across all affected methods

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
Source/Testably.Abstractions.Testing/FileSystem/FileMock.cs	Refactored file write/append methods to use UTF-8 as default and consolidated logic into WriteText helper
Tests/Testably.Abstractions.Tests/FileSystem/File/WriteAllTextTests.cs	Added tests verifying UTF-8 encoding and improved code formatting
Tests/Testably.Abstractions.Tests/FileSystem/File/WriteAllTextAsyncTests.cs	Added tests for async text writing with UTF-8 encoding verification
Tests/Testably.Abstractions.Tests/FileSystem/File/WriteAllLinesTests.cs	Added tests for line writing methods with UTF-8 encoding verification
Tests/Testably.Abstractions.Tests/FileSystem/File/WriteAllLinesAsyncTests.cs	Added tests for async line writing with UTF-8 encoding and improved formatting
Tests/Testably.Abstractions.Tests/FileSystem/File/AppendAllTextTests.cs	Added tests for text appending with UTF-8 encoding verification
Tests/Testably.Abstractions.Tests/FileSystem/File/AppendAllTextAsyncTests.cs	Added tests for async text appending with UTF-8 encoding verification
Tests/Testably.Abstractions.Tests/FileSystem/File/AppendAllLinesTests.cs	Added tests for line appending with UTF-8 encoding verification
Tests/Testably.Abstractions.Tests/FileSystem/File/AppendAllLinesAsyncTests.cs	Added tests for async line appending with UTF-8 encoding verification

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
97.5% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Test Results

    37 files  ±  0      37 suites  ±0   20m 45s ⏱️ -14s
44 075 tests +371  41 650 ✅ +371  2 425 💤 ±0  0 ❌ ±0 
85 682 runs  +372  76 695 ✅ +372  8 987 💤 ±0  0 ❌ ±0 

Results for commit dddacdf. ± Comparison against base commit 78b0421.

This pull request removes 35765 and adds 36136 tests. Note that renamed tests count towards both.

Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path01d46b97-9347-4592-a1bf-36454d0cc931")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path237e1037-63df-4e0a-aaee-58aead07239c")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path67e5fcfc-542c-4f05-9683-85bbcc6fa56c")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "patha28c2a20-0c0b-4b87-954c-37b6fbd56f74")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "patha385e8be-4c27-4f30-bc44-cd8fa9b27e60")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "pathbf34c1dd-f9d2-48bc-98d5-bed94f3d9363")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "pathdc6ac87b-4b9f-49bc-8ad6-5a6a8994c106")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path1d4d700d-d508-49e8-b120-d6c9237790de")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path274bf425-4ec7-474f-947b-2af6ef7b4a34")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path32b2716d-938c-4ba2-8488-de84719f3db5")
…

Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path0a226c94-820a-4f6c-8fef-4e8f48b2f8c0")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path0b6818b2-7ed5-410d-93e0-16d5c5ae9e2a")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path7eea03f2-2347-4a76-b9dc-c15572c0e0bf")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path99a81b76-453b-46c9-aa24-e45559b45692")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "pathb2a0e310-3bbd-4e2a-a233-664e6d543876")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "pathb65fc3d1-84f5-4de7-8913-9e64f07e1bb0")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "pathdb932a9a-4221-4a07-84f6-a1a81a4ff132")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path34243ace-650d-4242-bb17-58ac9c7ab9b1")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path3bb609b1-f9f0-4e68-ad3b-36da6122fd6b")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path6ebbf531-25dc-4a11-9dcf-5187bf716e45")
…

This pull request removes 1784 skipped tests and adds 1784 skipped tests. Note that renamed tests count towards both.

Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path01d46b97-9347-4592-a1bf-36454d0cc931")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path237e1037-63df-4e0a-aaee-58aead07239c")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "patha28c2a20-0c0b-4b87-954c-37b6fbd56f74")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "patha385e8be-4c27-4f30-bc44-cd8fa9b27e60")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path1d4d700d-d508-49e8-b120-d6c9237790de")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path32b2716d-938c-4ba2-8488-de84719f3db5")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path7b1f4a05-a9fb-4c7b-b054-5ad28604a6fb")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "pathb8c46517-0da4-4cce-a6a6-bb741df22da6")
Testably.Abstractions.Testing.Tests.FileSystem.FileMockTests ‑ GetUnixFileMode_SafeFileHandle_ShouldThrowPlatformNotSupportedExceptionOnWindows(path: "path34e2ccd4-4be6-4078-9fad-7d1d25abca7c")
Testably.Abstractions.Testing.Tests.FileSystem.FileMockTests ‑ GetUnixFileMode_SafeFileHandle_ShouldThrowPlatformNotSupportedExceptionOnWindows(path: "path7bf753fa-381d-4080-bef5-2dcf10d65238")
…

Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path7eea03f2-2347-4a76-b9dc-c15572c0e0bf")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path99a81b76-453b-46c9-aa24-e45559b45692")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "pathb2a0e310-3bbd-4e2a-a233-664e6d543876")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+MockFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "pathdb932a9a-4221-4a07-84f6-a1a81a4ff132")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path34243ace-650d-4242-bb17-58ac9c7ab9b1")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path3bb609b1-f9f0-4e68-ad3b-36da6122fd6b")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "path8eb37fca-9779-4a47-bc1c-7c0f81b77b58")
Testably.Abstractions.AccessControl.Tests.DirectoryInfoAclExtensionsTests+RealFileSystemTests ‑ SetAccessControl_ShouldNotUpdateTimes(path: "pathfbea2c2d-1a59-4d6e-bebd-564bd94bfb3c")
Testably.Abstractions.Testing.Tests.FileSystem.FileMockTests ‑ GetUnixFileMode_SafeFileHandle_ShouldThrowPlatformNotSupportedExceptionOnWindows(path: "path443d2591-7d58-4ab6-9eba-9c92ad321cd3")
Testably.Abstractions.Testing.Tests.FileSystem.FileMockTests ‑ GetUnixFileMode_SafeFileHandle_ShouldThrowPlatformNotSupportedExceptionOnWindows(path: "path8f3e215b-13ff-4dee-81d6-037f98083523")
…

[github-actions]

This is addressed in release v4.3.3.