[Essentials] Make Locale constructible by external TextToSpeech backends

Microsoft.Maui-mac.slnf

@@ -45,6 +45,7 @@
       "src\\Essentials\\samples\\Samples\\Essentials.Sample.csproj",
       "src\\Essentials\\src\\Essentials.csproj",
       "src\\Essentials\\test\\DeviceTests\\Essentials.DeviceTests.csproj",
+      "src\\Essentials\\test\\ExternalBackendTests\\Essentials.ExternalBackend.UnitTests.csproj",
       "src\\Essentials\\test\\UnitTests\\Essentials.UnitTests.csproj",
       "src\\Graphics\\src\\Graphics.Skia\\Graphics.Skia.csproj",
       "src\\Graphics\\src\\Graphics\\Graphics.csproj",

Microsoft.Maui-windows.slnf

@@ -52,6 +52,7 @@
       "src\\Essentials\\samples\\Samples\\Essentials.Sample.csproj",
       "src\\Essentials\\src\\Essentials.csproj",
       "src\\Essentials\\test\\DeviceTests\\Essentials.DeviceTests.csproj",
+      "src\\Essentials\\test\\ExternalBackendTests\\Essentials.ExternalBackend.UnitTests.csproj",
       "src\\Essentials\\test\\UnitTests\\Essentials.UnitTests.csproj",
       "src\\Graphics\\samples\\GraphicsTester.Android\\GraphicsTester.Android.csproj",
       "src\\Graphics\\samples\\GraphicsTester.Portable\\GraphicsTester.Portable.csproj",

Microsoft.Maui.sln

@@ -95,6 +95,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Essentials.DeviceTests", "s
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Essentials.UnitTests", "src\Essentials\test\UnitTests\Essentials.UnitTests.csproj", "{A9BAB840-A53E-405A-9458-CA0E02319FB4}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Essentials.ExternalBackend.UnitTests", "src\Essentials\test\ExternalBackendTests\Essentials.ExternalBackend.UnitTests.csproj", "{7C6A0D6E-9B4E-4C0E-9E3C-2F1A5D8B4E71}"
+EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Controls.Maps", "src\Controls\Maps\src\Controls.Maps.csproj", "{5C40FA00-7D48-4F54-898C-01C8942E451D}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "test", "test", "{25D0D27A-C5FE-443D-8B65-D6C987F4A80E}"
@@ -368,6 +370,10 @@ Global
 		{A9BAB840-A53E-405A-9458-CA0E02319FB4}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{A9BAB840-A53E-405A-9458-CA0E02319FB4}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{A9BAB840-A53E-405A-9458-CA0E02319FB4}.Release|Any CPU.Build.0 = Release|Any CPU
+		{7C6A0D6E-9B4E-4C0E-9E3C-2F1A5D8B4E71}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{7C6A0D6E-9B4E-4C0E-9E3C-2F1A5D8B4E71}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{7C6A0D6E-9B4E-4C0E-9E3C-2F1A5D8B4E71}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{7C6A0D6E-9B4E-4C0E-9E3C-2F1A5D8B4E71}.Release|Any CPU.Build.0 = Release|Any CPU
 		{5C40FA00-7D48-4F54-898C-01C8942E451D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{5C40FA00-7D48-4F54-898C-01C8942E451D}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{5C40FA00-7D48-4F54-898C-01C8942E451D}.Release|Any CPU.ActiveCfg = Release|Any CPU
@@ -686,6 +692,7 @@ Global
 		{420BC8CC-EE70-49A1-964A-CB63414A882D} = {94F3C036-A5F4-4ACC-A028-8506802ADB88}
 		{66528BE6-FF53-4A3B-8675-46C0B929C83B} = {420BC8CC-EE70-49A1-964A-CB63414A882D}
 		{A9BAB840-A53E-405A-9458-CA0E02319FB4} = {420BC8CC-EE70-49A1-964A-CB63414A882D}
+		{7C6A0D6E-9B4E-4C0E-9E3C-2F1A5D8B4E71} = {420BC8CC-EE70-49A1-964A-CB63414A882D}
 		{5C40FA00-7D48-4F54-898C-01C8942E451D} = {50C758FE-4E10-409A-94F5-A75480960864}
 		{25D0D27A-C5FE-443D-8B65-D6C987F4A80E} = {459BF674-83CB-46F6-881F-A2D2117DBF4D}
 		{094FB109-1CBC-4B84-8CFB-072E7B3EC637} = {25D0D27A-C5FE-443D-8B65-D6C987F4A80E}

eng/cake/dotnet.cake

@@ -276,6 +276,7 @@ Task("dotnet-test")
             "**/Controls.BindingSourceGen.UnitTests.csproj",
             "**/Core.UnitTests.csproj",
             "**/Essentials.UnitTests.csproj",
+            "**/Essentials.ExternalBackend.UnitTests.csproj",
             "**/Resizetizer.UnitTests.csproj",
             "**/Graphics.Tests.csproj",
             "**/MauiBlazorWebView.UnitTests.csproj",

eng/helix.proj

@@ -51,6 +51,7 @@
     <XUnitProject Include="$(RepoRoot)src/Controls/tests/SourceGen.UnitTests/SourceGen.UnitTests.csproj" />
     <XUnitProject Include="$(RepoRoot)src/Core/tests/UnitTests/Core.UnitTests.csproj" />
     <XUnitProject Include="$(RepoRoot)src/Essentials/test/UnitTests/Essentials.UnitTests.csproj" />
+    <XUnitProject Include="$(RepoRoot)src/Essentials/test/ExternalBackendTests/Essentials.ExternalBackend.UnitTests.csproj" />
     <XUnitProject Include="$(RepoRoot)src/Graphics/tests/Graphics.Tests/Graphics.Tests.csproj" />
     <XUnitProject Include="$(RepoRoot)src/BlazorWebView/tests/MauiBlazorWebView.UnitTests/MauiBlazorWebView.UnitTests.csproj" />
   </ItemGroup>

src/Essentials/src/PublicAPI/net-android/PublicAPI.Unshipped.txt

@@ -63,3 +63,4 @@ static Microsoft.Maui.Authentication.Passkeys.CreateAsync(Microsoft.Maui.Authent
 static Microsoft.Maui.Authentication.Passkeys.CreateAsync(string! creationOptionsJson, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<Microsoft.Maui.Authentication.PasskeyCreationResponse!>!
 static Microsoft.Maui.Authentication.Passkeys.Default.get -> Microsoft.Maui.Authentication.IPasskeys!
 static Microsoft.Maui.Authentication.Passkeys.IsSupported.get -> bool
+Microsoft.Maui.Media.Locale.Locale(string? language, string? country, string? name, string? id) -> void

src/Essentials/src/PublicAPI/net-ios/PublicAPI.Unshipped.txt

@@ -50,3 +50,4 @@ static Microsoft.Maui.Authentication.Passkeys.CreateAsync(Microsoft.Maui.Authent
 static Microsoft.Maui.Authentication.Passkeys.CreateAsync(string! creationOptionsJson, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<Microsoft.Maui.Authentication.PasskeyCreationResponse!>!
 static Microsoft.Maui.Authentication.Passkeys.Default.get -> Microsoft.Maui.Authentication.IPasskeys!
 static Microsoft.Maui.Authentication.Passkeys.IsSupported.get -> bool
+Microsoft.Maui.Media.Locale.Locale(string? language, string? country, string? name, string? id) -> void

src/Essentials/src/PublicAPI/net-maccatalyst/PublicAPI.Unshipped.txt

@@ -50,3 +50,4 @@ static Microsoft.Maui.Authentication.Passkeys.CreateAsync(Microsoft.Maui.Authent
 static Microsoft.Maui.Authentication.Passkeys.CreateAsync(string! creationOptionsJson, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<Microsoft.Maui.Authentication.PasskeyCreationResponse!>!
 static Microsoft.Maui.Authentication.Passkeys.Default.get -> Microsoft.Maui.Authentication.IPasskeys!
 static Microsoft.Maui.Authentication.Passkeys.IsSupported.get -> bool
+Microsoft.Maui.Media.Locale.Locale(string? language, string? country, string? name, string? id) -> void

src/Essentials/src/PublicAPI/net-tizen/PublicAPI.Unshipped.txt

@@ -48,3 +48,4 @@ static Microsoft.Maui.Authentication.Passkeys.CreateAsync(Microsoft.Maui.Authent
 static Microsoft.Maui.Authentication.Passkeys.CreateAsync(string! creationOptionsJson, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<Microsoft.Maui.Authentication.PasskeyCreationResponse!>!
 static Microsoft.Maui.Authentication.Passkeys.Default.get -> Microsoft.Maui.Authentication.IPasskeys!
 static Microsoft.Maui.Authentication.Passkeys.IsSupported.get -> bool
+Microsoft.Maui.Media.Locale.Locale(string? language, string? country, string? name, string? id) -> void

src/Essentials/src/PublicAPI/net-windows/PublicAPI.Unshipped.txt

@@ -51,3 +51,4 @@ static Microsoft.Maui.Authentication.Passkeys.CreateAsync(Microsoft.Maui.Authent
 static Microsoft.Maui.Authentication.Passkeys.CreateAsync(string! creationOptionsJson, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<Microsoft.Maui.Authentication.PasskeyCreationResponse!>!
 static Microsoft.Maui.Authentication.Passkeys.Default.get -> Microsoft.Maui.Authentication.IPasskeys!
 static Microsoft.Maui.Authentication.Passkeys.IsSupported.get -> bool
+Microsoft.Maui.Media.Locale.Locale(string? language, string? country, string? name, string? id) -> void

src/Essentials/src/PublicAPI/net/PublicAPI.Unshipped.txt

@@ -48,3 +48,4 @@ static Microsoft.Maui.Authentication.Passkeys.CreateAsync(Microsoft.Maui.Authent
 static Microsoft.Maui.Authentication.Passkeys.CreateAsync(string! creationOptionsJson, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<Microsoft.Maui.Authentication.PasskeyCreationResponse!>!
 static Microsoft.Maui.Authentication.Passkeys.Default.get -> Microsoft.Maui.Authentication.IPasskeys!
 static Microsoft.Maui.Authentication.Passkeys.IsSupported.get -> bool
+Microsoft.Maui.Media.Locale.Locale(string? language, string? country, string? name, string? id) -> void

src/Essentials/src/PublicAPI/netstandard/PublicAPI.Unshipped.txt

@@ -48,3 +48,4 @@ static Microsoft.Maui.Authentication.Passkeys.CreateAsync(Microsoft.Maui.Authent
 static Microsoft.Maui.Authentication.Passkeys.CreateAsync(string! creationOptionsJson, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<Microsoft.Maui.Authentication.PasskeyCreationResponse!>!
 static Microsoft.Maui.Authentication.Passkeys.Default.get -> Microsoft.Maui.Authentication.IPasskeys!
 static Microsoft.Maui.Authentication.Passkeys.IsSupported.get -> bool
+Microsoft.Maui.Media.Locale.Locale(string? language, string? country, string? name, string? id) -> void

src/Essentials/src/TextToSpeech/TextToSpeech.android.cs

@@ -126,10 +126,10 @@ public async Task SpeakAsync(string text, int max, SpeechOptions options, Cancel
 				});
 			}
 
-			if (options?.Locale?.Language != null)
+			if (!string.IsNullOrEmpty(options?.Locale?.Language))
 			{
 				JavaLocale locale = null;
-				if (!string.IsNullOrWhiteSpace(options?.Locale.Country))
+				if (!string.IsNullOrWhiteSpace(options.Locale.Country))
 					locale = new JavaLocale(options.Locale.Language, options.Locale.Country);
 				else
 					locale = new JavaLocale(options.Locale.Language);

src/Essentials/src/TextToSpeech/TextToSpeech.ios.tvos.watchos.cs

@@ -31,7 +31,7 @@ static AVSpeechUtterance GetSpeechUtterance(string text, SpeechOptions options)
 				// null voice if fine - it is the default
 				// select the voice by identifier else by Language, otherwise set for default
 				speechUtterance.Voice =
-				    options.Locale?.Id != null
+				    !string.IsNullOrEmpty(options.Locale?.Id)
 				        ? AVSpeechSynthesisVoice.FromIdentifier(options.Locale.Id)
 				        : AVSpeechSynthesisVoice.FromLanguage(options.Locale?.Language)
 				        ?? AVSpeechSynthesisVoice.FromLanguage(AVSpeechSynthesisVoice.CurrentLanguageCode);

src/Essentials/src/TextToSpeech/TextToSpeech.macos.cs

@@ -30,7 +30,7 @@ async Task PlatformSpeakAsync(string text, SpeechOptions options, CancellationTo
 					if (options.Volume.HasValue)
 						ss.Volume = NormalizeVolume(options.Volume);
 
-					if (options.Locale != null)
+					if (!string.IsNullOrEmpty(options.Locale?.Id))
 						ss.Voice = options.Locale.Id;
 
 					if (options.Rate.HasValue)

src/Essentials/src/TextToSpeech/TextToSpeech.shared.cs

@@ -245,13 +245,31 @@ public async Task SpeakAsync(string text, SpeechOptions? options = default, Canc
 	/// <summary>
 	/// Represents a specific geographical, political, or cultural region.
 	/// </summary>
+	/// <remarks>
+	/// <para>
+	/// Instances are normally obtained from <see cref="ITextToSpeech.GetLocalesAsync"/>. The constructor is
+	/// public so that text-to-speech backends which live outside of .NET MAUI can implement
+	/// <see cref="ITextToSpeech"/> and return values that .NET MAUI understands.
+	/// </para>
+	/// <para>
+	/// The exact meaning of <see cref="Language"/>, <see cref="Country"/>, <see cref="Name"/> and <see cref="Id"/>
+	/// is defined by the text-to-speech engine that produced the locale, so values are stored verbatim: they are
+	/// not parsed, validated, trimmed, or case normalized. The only normalization performed is that
+	/// <see langword="null"/> is converted to <see cref="string.Empty"/>, so every property is guaranteed to be
+	/// non-<see langword="null"/>.
+	/// </para>
+	/// <para>
+	/// Locales are immutable and use reference equality; two instances created with identical values are not
+	/// considered equal.
+	/// </para>
+	/// </remarks>
 	public class Locale
 	{
 		/// <summary>
 		/// Gets the language name or code.
 		/// </summary>
 		/// <remarks>
-		/// <para>This value may vary between platforms.</para>
+		/// <para>This value may vary between platforms and is never <see langword="null"/>; an unknown language is represented by <see cref="string.Empty"/>.</para>
 		/// <para>
 		/// For Android this used the ISO 639 alpha-2 or alpha-3 language code, or registered language subtags up to 8 alpha letters (for future enhancements).
 		/// When a language has both an alpha-2 code and an alpha-3 code, the alpha-2 code must be used.
@@ -264,28 +282,44 @@ public class Locale
 		/// Gets the country name or code.
 		/// </summary>
 		/// <remarks>
-		/// <para>This value may vary between platforms.</para>
+		/// <para>This value may vary between platforms and is never <see langword="null"/>; an unknown or unused country is represented by <see cref="string.Empty"/>.</para>
 		/// <para>For Android this used the ISO 3166 alpha-2 country code or UN M.49 numeric-3 area code.</para>
-		/// <para>For iOS and Windows this field is not used and <see langword="null"/> .</para>
+		/// <para>For iOS and Windows this field is not used and is <see cref="string.Empty"/>. On those platforms the region is already part of <see cref="Language"/> (for example <c>en-US</c>).</para>
 		/// </remarks>
 		public string Country { get; }
 
 		/// <summary>
 		/// Gets the display name of the locale.
 		/// </summary>
+		/// <remarks>This value is never <see langword="null"/>; engines that do not provide a display name report <see cref="string.Empty"/>.</remarks>
 		public string Name { get; }
 
 		/// <summary>
 		/// Gets the unique identifier of the locale.
 		/// </summary>
+		/// <remarks>
+		/// <para>This identifier is only meaningful to the text-to-speech engine that produced it and is never <see langword="null"/>; engines that do not expose an identifier report <see cref="string.Empty"/>.</para>
+		/// <para>When this value is empty, platforms fall back to selecting a voice using <see cref="Language"/> and <see cref="Country"/>.</para>
+		/// </remarks>
 		public string Id { get; }
 
-		internal Locale(string language, string country, string name, string id)
+		/// <summary>
+		/// Initializes a new instance of the <see cref="Locale"/> class.
+		/// </summary>
+		/// <param name="language">The language name or code, as described by <see cref="Language"/>.</param>
+		/// <param name="country">The country name or code, as described by <see cref="Country"/>. Pass <see langword="null"/> when the language already carries the region, or when the engine does not report one.</param>
+		/// <param name="name">The display name of the locale, as described by <see cref="Name"/>.</param>
+		/// <param name="id">The engine specific identifier of the locale, as described by <see cref="Id"/>.</param>
+		/// <remarks>
+		/// No argument is required and none are validated. A <see langword="null"/> argument is normalized to
+		/// <see cref="string.Empty"/>; every other value is stored exactly as supplied.
+		/// </remarks>
+		public Locale(string? language, string? country, string? name, string? id)
 		{
-			Language = language;
-			Country = country;
-			Name = name;
-			Id = id;
+			Language = language ?? string.Empty;
+			Country = country ?? string.Empty;
+			Name = name ?? string.Empty;
+			Id = id ?? string.Empty;
 		}
 	}
 

src/Essentials/src/TextToSpeech/TextToSpeech.tizen.cs

@@ -29,7 +29,7 @@ async Task PlatformSpeakAsync(string text, SpeechOptions options, CancellationTo
 
 			var language = "en_US";
 			var voiceType = Voice.Auto;
-			if (options?.Locale.Language != null)
+			if (!string.IsNullOrEmpty(options?.Locale?.Language))
 			{
 				foreach (var voice in tts.GetSupportedVoices())
 				{

src/Essentials/test/ExternalBackendTests/Essentials.ExternalBackend.UnitTests.csproj

@@ -0,0 +1,29 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <!--
+    This project intentionally does NOT have InternalsVisibleTo access to
+    Microsoft.Maui.Essentials. It exists to prove that an out-of-tree platform
+    backend (for example a community Tizen backend) can implement ITextToSpeech
+    using only the public Essentials API surface.
+  -->
+  <PropertyGroup>
+    <TargetFramework>$(_MauiDotNetTfm)</TargetFramework>
+    <IsPackable>false</IsPackable>
+    <AssemblyName>Microsoft.Maui.Essentials.ExternalBackend.UnitTests</AssemblyName>
+    <Configurations>Debug;Release</Configurations>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(Configuration)'=='Debug' ">
+    <DebugSymbols>true</DebugSymbols>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="xunit" Version="$(XunitPackageVersion)" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Essentials.csproj" />
+  </ItemGroup>
+
+</Project>

src/Essentials/test/ExternalBackendTests/ExternalTextToSpeechBackendTests.cs

@@ -0,0 +1,118 @@
+#nullable enable
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Maui.Media;
+using Xunit;
+
+namespace Microsoft.Maui.Essentials.ExternalBackend.UnitTests
+{
+	/// <summary>
+	/// Stands in for an out-of-tree platform backend (for example a community Tizen
+	/// backend). It is compiled into an assembly that has no <c>InternalsVisibleTo</c>
+	/// access to Microsoft.Maui.Essentials, so it can only use the public API surface.
+	/// </summary>
+	sealed class ExternalTextToSpeech : ITextToSpeech
+	{
+		public SpeechOptions? LastOptions { get; private set; }
+
+		public Task<IEnumerable<Locale>> GetLocalesAsync() =>
+			Task.FromResult<IEnumerable<Locale>>(new[]
+			{
+				new Locale("en", "US", "English (United States)", "external:en-US"),
+				new Locale("ko", "KR", "Korean (Korea)", "external:ko-KR"),
+
+				// A backend that can only report a language uses null for the rest.
+				new Locale("fr", null, null, null),
+			});
+
+		public Task SpeakAsync(string text, SpeechOptions? options = default, CancellationToken cancelToken = default)
+		{
+			LastOptions = options;
+			return Task.CompletedTask;
+		}
+	}
+
+	public class ExternalTextToSpeechBackendTests
+	{
+		[Fact]
+		public void LocaleConstructorIsAccessibleOutsideEssentials()
+		{
+			var locale = new Locale("en", "US", "English (United States)", "external:en-US");
+
+			Assert.Equal("en", locale.Language);
+			Assert.Equal("US", locale.Country);
+			Assert.Equal("English (United States)", locale.Name);
+			Assert.Equal("external:en-US", locale.Id);
+		}
+
+		[Theory]
+		[InlineData(null)]
+		[InlineData("")]
+		public void NullAndEmptyValuesNormalizeToEmptyString(string? value)
+		{
+			var locale = new Locale(value!, value, value, value);
+
+			Assert.Equal(string.Empty, locale.Language);
+			Assert.Equal(string.Empty, locale.Country);
+			Assert.Equal(string.Empty, locale.Name);
+			Assert.Equal(string.Empty, locale.Id);
+		}
+
+		[Fact]
+		public void ValuesAreNotTrimmedOrCaseNormalized()
+		{
+			var locale = new Locale("EN", "us", " Display ", "Id");
+
+			Assert.Equal("EN", locale.Language);
+			Assert.Equal("us", locale.Country);
+			Assert.Equal(" Display ", locale.Name);
+			Assert.Equal("Id", locale.Id);
+		}
+
+		[Fact]
+		public async Task ExternalBackendCanReturnLocalesFromGetLocalesAsync()
+		{
+			ITextToSpeech tts = new ExternalTextToSpeech();
+
+			var locales = (await tts.GetLocalesAsync()).ToList();
+
+			Assert.Equal(3, locales.Count);
+			Assert.Contains(locales, l => l.Language == "en" && l.Country == "US");
+			Assert.Contains(locales, l => l.Language == "ko" && l.Id == "external:ko-KR");
+
+			// Language-only locales still expose non-null property values.
+			var languageOnly = Assert.Single(locales, l => l.Language == "fr");
+			Assert.Equal(string.Empty, languageOnly.Country);
+			Assert.Equal(string.Empty, languageOnly.Name);
+			Assert.Equal(string.Empty, languageOnly.Id);
+		}
+
+		[Fact]
+		public async Task ExternalBackendCanRoundTripLocaleThroughSpeechOptions()
+		{
+			var backend = new ExternalTextToSpeech();
+			ITextToSpeech tts = backend;
+
+			var locale = (await tts.GetLocalesAsync()).First();
+
+			await tts.SpeakAsync("hello", new SpeechOptions { Locale = locale, Rate = 1.0f });
+
+			Assert.NotNull(backend.LastOptions);
+			Assert.Same(locale, backend.LastOptions!.Locale);
+			Assert.Equal("en", backend.LastOptions.Locale!.Language);
+		}
+
+		[Fact]
+		public void LocaleUsesReferenceEqualityAndDefaultToString()
+		{
+			var first = new Locale("en", "US", "English (United States)", "external:en-US");
+			var second = new Locale("en", "US", "English (United States)", "external:en-US");
+
+			Assert.NotEqual(first, second);
+			Assert.Equal(first, first);
+			Assert.Equal(typeof(Locale).FullName, first.ToString());
+		}
+	}
+}