Add documentation for MSTEST0050 analyzer rule

Co-authored-by: Youssef1313 <[email protected]>

Author: Copilot

docs/core/testing/mstest-analyzers/mstest0050.md

@@ -0,0 +1,81 @@
+---
+title: "MSTEST0050: Global test fixture should be valid"
+description: "Learn about code analysis rule MSTEST0050: Global test fixture should be valid"
+ms.date: 07/29/2025
+f1_keywords:
+- MSTEST0050
+- GlobalTestFixtureShouldBeValidAnalyzer
+helpviewer_keywords:
+- GlobalTestFixtureShouldBeValidAnalyzer
+- MSTEST0050
+author: Evangelink
+ms.author: amauryleve
+---
+# MSTEST0050: Global test fixture should be valid
+
+| Property                            | Value                                                                                    |
+|-------------------------------------|------------------------------------------------------------------------------------------|
+| **Rule ID**                         | MSTEST0050                                                                               |
+| **Title**                           | Global test fixture should be valid                                                     |
+| **Category**                        | Usage                                                                                    |
+| **Fix is breaking or non-breaking** | Non-breaking                                                                             |
+| **Enabled by default**              | Yes                                                                                      |
+| **Default severity**                | Warning                                                                                  |
+| **Introduced in version**           | 3.10.0                                                                                   |
+| **Is there a code fix**             | Yes                                                                                      |
+
+## Cause
+
+A global test fixture method (marked with <xref:Microsoft.VisualStudio.TestTools.UnitTesting.AssemblyInitializeAttribute> or <xref:Microsoft.VisualStudio.TestTools.UnitTesting.AssemblyCleanupAttribute>) doesn't follow the required layout or has invalid configuration.
+
+## Rule description
+
+Global test fixture methods must follow specific requirements to ensure proper test execution. This rule validates that methods marked with <xref:Microsoft.VisualStudio.TestTools.UnitTesting.AssemblyInitializeAttribute> or <xref:Microsoft.VisualStudio.TestTools.UnitTesting.AssemblyCleanupAttribute> adhere to the correct method signature and configuration rules.
+
+Common violations include:
+
+- Incorrect method signatures or parameters
+- Invalid access modifiers
+- Missing or incorrect return types
+- Improper method declarations
+
+## How to fix violations
+
+Ensure that global test fixture methods follow the required layout:
+
+- Methods marked with <xref:Microsoft.VisualStudio.TestTools.UnitTesting.AssemblyInitializeAttribute> should be `public static` and take a <xref:Microsoft.VisualStudio.TestTools.UnitTesting.TestContext> parameter
+- Methods marked with <xref:Microsoft.VisualStudio.TestTools.UnitTesting.AssemblyCleanupAttribute> should be `public static` and optionally take a <xref:Microsoft.VisualStudio.TestTools.UnitTesting.TestContext> parameter (starting with MSTest 3.6)
+
+## When to suppress warnings
+
+Don't suppress warnings from this rule. Global test fixture methods with invalid layouts may not execute properly or may cause runtime errors.
+
+## Example of a violation
+
+```csharp
+[TestClass]
+public class GlobalTestFixture
+{
+    // Violation: AssemblyInitialize method should be static and take TestContext parameter
+    [AssemblyInitialize]
+    public void Setup()
+    {
+        // Setup code
+    }
+}
+```
+
+## Example of how to fix
+
+```csharp
+[TestClass]
+public class GlobalTestFixture
+{
+    // Fixed: Correct method signature for AssemblyInitialize
+    [AssemblyInitialize]
+    public static void Setup(TestContext testContext)
+    {
+        // Setup code
+    }
+}
+```

docs/core/testing/mstest-analyzers/usage-rules.md

@@ -43,3 +43,4 @@ Identifier | Name | Description
 [MSTEST0046](mstest0046.md) | StringAssertToAssertAnalyzer | A test method uses <xref:Microsoft.VisualStudio.TestTools.UnitTesting.StringAssert> methods instead of equivalent <xref:Microsoft.VisualStudio.TestTools.UnitTesting.Assert> methods.
 [MSTEST0048](mstest0048.md) | TestContextPropertyUsageAnalyzer | A fixture method (methods with <xref:Microsoft.VisualStudio.TestTools.UnitTesting.AssemblyInitializeAttribute>, <xref:Microsoft.VisualStudio.TestTools.UnitTesting.AssemblyCleanupAttribute>, <xref:Microsoft.VisualStudio.TestTools.UnitTesting.ClassInitializeAttribute>, or <xref:Microsoft.VisualStudio.TestTools.UnitTesting.ClassCleanupAttribute>) accesses restricted <xref:Microsoft.VisualStudio.TestTools.UnitTesting.TestContext> properties.
 [MSTEST0049](mstest0049.md) | FlowTestContextCancellationTokenAnalyzer | A method call within a test context doesn't use the <xref:System.Threading.CancellationToken> available from <xref:Microsoft.VisualStudio.TestTools.UnitTesting.TestContext> when the called method has a parameter or overload that accepts a <xref:System.Threading.CancellationToken>.
+[MSTEST0050](mstest0050.md) | GlobalTestFixtureShouldBeValidAnalyzer | A global test fixture method (marked with <xref:Microsoft.VisualStudio.TestTools.UnitTesting.AssemblyInitializeAttribute> or <xref:Microsoft.VisualStudio.TestTools.UnitTesting.AssemblyCleanupAttribute>) doesn't follow the required layout or has invalid configuration.