MSTEST0061: Use OSCondition attribute instead of runtime checks

Cause

A test method uses IsOSPlatform(OSPlatform) checks with an early return instead of the OSConditionAttribute attribute.

Rule description

When you want to skip tests based on the operating system, use the OSConditionAttribute attribute instead of manual runtime checks. The attribute approach provides better test discoverability and clearer test intent, and integrates properly with test frameworks to mark tests as skipped rather than passed.

using System.Runtime.InteropServices;

[TestClass]
public class TestClass
{
    [TestMethod]
    public void TestMethod()
    {
        if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) // Violation
        {
            return;
        }
        
        // Test code that requires Windows
    }
}

How to fix violations

Replace the runtime check with the [OSCondition] attribute.

using Microsoft.VisualStudio.TestTools.UnitTesting;

[TestClass]
public class TestClass
{
    [TestMethod]
    [OSCondition(OperatingSystems.Windows)]
    public void TestMethod()
    {
        // Test code that requires Windows
    }
}

The [OSCondition] attribute supports the following operating systems:

• OperatingSystems.Linux
• OperatingSystems.OSX (macOS)
• OperatingSystems.Windows
• OperatingSystems.FreeBSD

You can also combine multiple operating systems using bitwise OR:

[TestMethod]
[OSCondition(OperatingSystems.Windows | OperatingSystems.Linux)]
public void TestMethod()
{
    // Test code that requires Windows or Linux
}

When to suppress warnings

You might suppress this warning if your runtime check is more complex than a simple early return pattern, or if you need to perform conditional logic that cannot be expressed using the [OSCondition] attribute.

Suppress a warning

If you just want to suppress a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

#pragma warning disable MSTEST0061
// The code that's violating the rule is on this line.
#pragma warning restore MSTEST0061

To disable the rule for a file, folder, or project, set its severity to none in the configuration file.

[*.{cs,vb}]
dotnet_diagnostic.MSTEST0061.severity = none

For more information, see How to suppress code analysis warnings.