Add skipping tests based on the [SupportedOSPlatform] attribute

README.md

@@ -38,4 +38,23 @@ public void TestFunctionalityWhichIsNotSupportedOnSomePlatforms()
 }
 ```
 
+## The `[SupportedOSPlatform]` attribute
+
+Since version 1.5, `Xunit.SkippableFact` understands the `SupportedOSPlatform` attribute to skip tests on unsupported platforms.
+
+```csharp
+[SkippableFact, SupportedOSPlatform("Windows")]
+public void TestCngKey()
+{
+    var key = CngKey.Create(CngAlgorithm.Sha256);
+    Assert.NotNull(key);
+}
+```
+
+Without `[SupportedOSPlatform("Windows")]` the [CA1416][CA1416] code analysis warning would trigger:
+> This call site is reachable on all platforms. 'CngKey. Create(CngAlgorithm)' is only supported on: 'windows'.
+
+Adding `[SupportedOSPlatform("Windows")]` both suppresses this platform compatibility warning and skips the test when running on Linux or macOS.
+
 [NuPkg]: https://www.nuget.org/packages/Xunit.SkippableFact
+[CA1416]: https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1416

src/Xunit.SkippableFact/Sdk/SkippableFactTestCase.cs

@@ -88,4 +88,10 @@ public override void Deserialize(IXunitSerializationInfo data)
         base.Deserialize(data);
         this.SkippingExceptionNames = data.GetValue<string[]>(nameof(this.SkippingExceptionNames));
     }
+
+    /// <inheritdoc/>
+    protected override string GetSkipReason(IAttributeInfo factAttribute)
+    {
+        return this.TestMethod.GetPlatformSkipReason() ?? base.GetSkipReason(factAttribute);
+    }
 }

src/Xunit.SkippableFact/Sdk/SkippableTheoryTestCase.cs

@@ -86,4 +86,10 @@ public override void Deserialize(IXunitSerializationInfo data)
         base.Deserialize(data);
         this.SkippingExceptionNames = data.GetValue<string[]>(nameof(this.SkippingExceptionNames));
     }
+
+    /// <inheritdoc/>
+    protected override string GetSkipReason(IAttributeInfo factAttribute)
+    {
+        return this.TestMethod.GetPlatformSkipReason() ?? base.GetSkipReason(factAttribute);
+    }
 }

src/Xunit.SkippableFact/Sdk/TestMethodExtensions.cs

@@ -0,0 +1,129 @@
+// Copyright (c) Andrew Arnott. All rights reserved.
+// Licensed under the Microsoft Public License (Ms-PL). See LICENSE.txt file in the project root for full license information.
+
+using System.Runtime.InteropServices;
+using Xunit.Abstractions;
+
+namespace Xunit.Sdk;
+
+/// <summary>
+/// Extensions methods on <see cref="ITestMethod"/>.
+/// </summary>
+internal static class TestMethodExtensions
+{
+    /// <summary>
+    /// Assesses whether the test method can run on the current platform by looking at the <c>[SupportedOSPlatform]</c> attributes on the test method and on the test class.
+    /// </summary>
+    /// <param name="testMethod">The <see cref="ITestMethod"/>.</param>
+    /// <returns>A description of the supported platforms if the test can not run on the current platform or <see langword="null"/> if the test can run on the current platform.</returns>
+    internal static string? GetPlatformSkipReason(this ITestMethod testMethod)
+    {
+#if NET462
+        return null;
+#else
+        HashSet<string> unsupportedPlatforms = GetPlatforms(testMethod, "UnsupportedOSPlatform");
+        string? unsupportedPlatform = unsupportedPlatforms.FirstOrDefault(MatchesCurrentPlatform);
+        if (unsupportedPlatform is not null)
+        {
+            return $"Unsupported on {unsupportedPlatform}";
+        }
+
+        HashSet<string> supportedPlatforms = GetPlatforms(testMethod, "SupportedOSPlatform");
+        if (supportedPlatforms.Count == 0 || supportedPlatforms.Any(MatchesCurrentPlatform))
+        {
+            return null;
+        }
+
+        string platformsDescription = supportedPlatforms.Count == 1 ? supportedPlatforms.First() : string.Join(", ", supportedPlatforms.Reverse().Skip(1).Reverse()) + " and " + supportedPlatforms.Last();
+        return $"Only supported on {platformsDescription}";
+#endif
+    }
+
+#if !NET462
+    private static bool MatchesCurrentPlatform(string platform)
+    {
+        int versionIndex = platform.IndexOfAny(['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']);
+        bool matchesVersion;
+        if (versionIndex >= 0 && Version.TryParse(platform[versionIndex..], out Version version))
+        {
+            platform = platform[..versionIndex];
+            matchesVersion = MatchesCurrentVersion(version.Major, version.Minor, version.Build, version.Revision);
+        }
+        else
+        {
+            matchesVersion = true;
+        }
+
+        return matchesVersion && RuntimeInformation.IsOSPlatform(OSPlatform.Create(platform));
+    }
+
+    // Adapted from OperatingSystem.IsOSVersionAtLeast() which is private, see https://github.com/dotnet/runtime/blob/d6eb35426ebdb09ee5c754aa9afb9ad6e96a3dec/src/libraries/System.Private.CoreLib/src/System/OperatingSystem.cs#L326-L351
+    private static bool MatchesCurrentVersion(int major, int minor, int build, int revision)
+    {
+        Version current = Environment.OSVersion.Version;
+
+        if (current.Major != major)
+        {
+            return current.Major > major;
+        }
+
+        if (current.Minor != minor)
+        {
+            return current.Minor > minor;
+        }
+
+        // Unspecified build component is to be treated as zero
+        int currentBuild = current.Build < 0 ? 0 : current.Build;
+        build = build < 0 ? 0 : build;
+        if (currentBuild != build)
+        {
+            return currentBuild > build;
+        }
+
+        // Unspecified revision component is to be treated as zero
+        int currentRevision = current.Revision < 0 ? 0 : current.Revision;
+        revision = revision < 0 ? 0 : revision;
+
+        return currentRevision >= revision;
+    }
+
+    /// <summary>
+    /// Returns the collection of platforms defined by the specified <paramref name="platformAttributeName"/> that decorate the test method and the test class.
+    /// </summary>
+    /// <param name="testMethod">The <see cref="ITestMethod"/>.</param>
+    /// <param name="platformAttributeName">Either <c>SupportedOSPlatform</c> or <c>UnsupportedOSPlatform</c>.</param>
+    /// <example>
+    /// <para>
+    /// Calling GetPlatforms(testMethod, "SupportedOSPlatform") where <paramref name="testMethod"/> represents <c>MyTest</c> returns ["Linux", "macOS"].
+    /// </para>
+    /// <code>
+    /// [SupportedOSPlatform("macOS")]
+    /// public class MyTests
+    /// {
+    ///     [SkippableFact]
+    ///     [SupportedOSPlatform("Linux")]
+    ///     public void MyTest()
+    ///     {
+    ///     }
+    /// }
+    /// </code>
+    /// </example>
+    /// <returns>The collection of platforms defined by the specified <paramref name="platformAttributeName"/> that decorate the test method and the test class.</returns>
+    private static HashSet<string> GetPlatforms(ITestMethod testMethod, string platformAttributeName)
+    {
+        string platformAttribute = $"System.Runtime.Versioning.{platformAttributeName}Attribute";
+        var platforms = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+        AddPlatforms(platforms, testMethod.Method.GetCustomAttributes(platformAttribute));
+        AddPlatforms(platforms, testMethod.Method.Type.GetCustomAttributes(platformAttribute));
+        return platforms;
+    }
+
+    private static void AddPlatforms(HashSet<string> platforms, IEnumerable<IAttributeInfo> supportedPlatformAttributes)
+    {
+        foreach (IAttributeInfo supportedPlatformAttribute in supportedPlatformAttributes)
+        {
+            platforms.Add(supportedPlatformAttribute.GetNamedArgument<string>("PlatformName"));
+        }
+    }
+#endif
+}

test/Xunit.SkippableFact.Tests/SampleTests.cs

@@ -1,7 +1,7 @@
 // Copyright (c) Andrew Arnott. All rights reserved.
 // Licensed under the Microsoft Public License (Ms-PL). See LICENSE.txt file in the project root for full license information.
 
-using System;
+using System.Runtime.Versioning;
 
 namespace Xunit.SkippableFact.Tests;
 
@@ -76,4 +76,77 @@ public void SkipInsideAssertThrows()
             throw new Exception();
         }));
     }
+
+#if NET5_0_OR_GREATER
+    [SkippableFact, SupportedOSPlatform("Linux")]
+    public void LinuxOnly()
+    {
+        Assert.True(OperatingSystem.IsLinux(), "This should only run on Linux");
+    }
+
+    [SkippableFact, SupportedOSPlatform("macOS")]
+    public void MacOsOnly()
+    {
+        Assert.True(OperatingSystem.IsMacOS(), "This should only run on macOS");
+    }
+
+    [SkippableFact, SupportedOSPlatform("macOS10.6")]
+    public void MacOs10_6Minimum()
+    {
+        Assert.True(OperatingSystem.IsMacOSVersionAtLeast(10, 6), "This should only run on macOS 10.6 onwards");
+    }
+
+    [SkippableFact, SupportedOSPlatform("macOS77.7")]
+    public void MacOs77_7Minimum()
+    {
+        Assert.True(OperatingSystem.IsMacOSVersionAtLeast(77, 7), "This should only run on macOS 77.7 onwards");
+    }
+
+    [SkippableFact, SupportedOSPlatform("Windows")]
+    public void WindowsOnly()
+    {
+        Assert.True(OperatingSystem.IsWindows(), "This should only run on Windows");
+    }
+
+    [SkippableFact, SupportedOSPlatform("Windows10.0")]
+    public void Windows10Minimum()
+    {
+        Assert.True(OperatingSystem.IsWindowsVersionAtLeast(10), "This should only run on Windows 10.0 onwards");
+    }
+
+    [SkippableFact, SupportedOSPlatform("Windows77.7")]
+    public void Windows77_7Minimum()
+    {
+        Assert.True(OperatingSystem.IsWindowsVersionAtLeast(77, 7), "This should only run on Windows 77.7 onwards");
+    }
+
+    [SkippableFact, SupportedOSPlatform("Android"), SupportedOSPlatform("Browser")]
+    public void AndroidAndBrowserFact()
+    {
+        Assert.True(OperatingSystem.IsAndroid() || OperatingSystem.IsBrowser(), "This should only run on Android and Browser");
+    }
+
+    [SkippableTheory, SupportedOSPlatform("Android"), SupportedOSPlatform("Browser")]
+    [InlineData(1)]
+    [InlineData(2)]
+    public void AndroidAndBrowserTheory(int number)
+    {
+        _ = number;
+        Assert.True(OperatingSystem.IsAndroid() || OperatingSystem.IsBrowser(), "This should only run on Android and Browser");
+    }
+
+    [SkippableFact, SupportedOSPlatform("Android"), SupportedOSPlatform("Browser"), SupportedOSPlatform("Wasi")]
+    public void AndroidAndBrowserAndWasiOnly()
+    {
+        Assert.True(OperatingSystem.IsAndroid() || OperatingSystem.IsBrowser() || OperatingSystem.IsWasi(), "This should only run on Android, Browser and Wasi");
+    }
+
+    [SkippableFact, UnsupportedOSPlatform("Linux"), UnsupportedOSPlatform("macOS"), UnsupportedOSPlatform("Windows")]
+    public void UnsupportedPlatforms()
+    {
+        Assert.False(OperatingSystem.IsLinux());
+        Assert.False(OperatingSystem.IsMacOS());
+        Assert.False(OperatingSystem.IsWindows());
+    }
+#endif
 }