Add check that tests are public

src/tests/Common/XUnitWrapperGenerator/Descriptors.cs

@@ -27,4 +27,22 @@ public static class Descriptors
             "XUnitWrapperGenerator",
             DiagnosticSeverity.Warning,
             isEnabledByDefault: true);
+
+    public static readonly DiagnosticDescriptor XUWG1003 =
+        new DiagnosticDescriptor(
+            "XUW1003",
+            "Test methods must be public",
+            "Test methods must be public. Add or change the visibility modifier of the test method to public.",
+            "XUnitWrapperGenerator",
+            DiagnosticSeverity.Error,
+            isEnabledByDefault: true);
+
+    public static readonly DiagnosticDescriptor XUWG1004 =
+        new DiagnosticDescriptor(
+            "XUW1004",
+            "Test classes must be public",
+            "Test classes must be public. Add or change the visibility modifier of the test class to public.",
+            "XUnitWrapperGenerator",
+            DiagnosticSeverity.Error,
+            isEnabledByDefault: true);
 }

src/tests/Common/XUnitWrapperGenerator/XUnitWrapperGenerator.cs

@@ -165,6 +165,49 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
                 context.ReportDiagnostic(Diagnostic.Create(Descriptors.XUWG1002, method.Locations[0]));
             });
 
+        context.RegisterImplementationSourceOutput(
+            methodsInSource
+            .Combine(context.AnalyzerConfigOptionsProvider)
+            .Where(data =>
+            {
+                var (_, configOptions) = data;
+                return configOptions.GlobalOptions.InMergedTestDirectory();
+            }),
+            static (context, data) =>
+            {
+                var (method, _) = data;
+
+                bool found = false;
+                foreach (var attr in method.GetAttributesOnSelfAndContainingSymbols())
+                {
+                    switch (attr.AttributeClass?.ToDisplayString())
+                    {
+                        case "Xunit.ConditionalFactAttribute":
+                        case "Xunit.FactAttribute":
+                        case "Xunit.ConditionalTheoryAttribute":
+                        case "Xunit.TheoryAttribute":
+                            found = true;
+                            break;
+                    }
+                }
+                if (!found) return;
+
+                if (method.DeclaredAccessibility != Accessibility.Public)
+                {
+                    context.ReportDiagnostic(Diagnostic.Create(Descriptors.XUWG1003, method.Locations[0]));
+                }
+
+                INamedTypeSymbol containingType = method.ContainingType;
+                while (containingType != null)
+                {
+                    if (containingType.DeclaredAccessibility != Accessibility.Public)
+                    {
+                        context.ReportDiagnostic(Diagnostic.Create(Descriptors.XUWG1004, method.Locations[0]));
+                    }
+                    containingType = containingType.ContainingType;
+                }
+            });
+
         context.RegisterImplementationSourceOutput(
             allTests
             .Combine(context.AnalyzerConfigOptionsProvider)

src/tests/JIT/Regression/JitBlue/GitHub_11408/GitHub_11408.cs

@@ -5,7 +5,7 @@
 using System.Runtime.CompilerServices;
 using Xunit;
 
-class GitHub_11408
+public class GitHub_11408
 {
     const int Pass = 100;
     const int Fail = -1;

src/tests/JIT/jit64/regress/vsw/528315/simple-repro.cs

@@ -2,20 +2,20 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using Xunit;
-internal enum NodeType
+public enum NodeType
 {
     True, False, Not, Other
 }
 
-internal class Node
+public class Node
 {
     public NodeType NodeType;
     public Node Child;
     public string name;
 
     public Node(string s) { name = s; }
 }
-internal class NodeFactory
+public class NodeFactory
 {
     public Node Conditional(Node condition, Node trueBranch, Node falseBranch)
     {