Update SA1133 tests for attributed local functions

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/ReadabilityRules/SA1133CSharp9UnitTests.cs

@@ -3,9 +3,70 @@
 
 namespace StyleCop.Analyzers.Test.CSharp9.ReadabilityRules
 {
+    using System.Threading;
+    using System.Threading.Tasks;
     using StyleCop.Analyzers.Test.CSharp8.ReadabilityRules;
+    using Xunit;
+    using static StyleCop.Analyzers.Test.Verifiers.StyleCopCodeFixVerifier<
+        StyleCop.Analyzers.ReadabilityRules.SA1133DoNotCombineAttributes,
+        StyleCop.Analyzers.ReadabilityRules.SA1133CodeFixProvider>;
 
     public partial class SA1133CSharp9UnitTests : SA1133CSharp8UnitTests
     {
+        [Fact]
+        [WorkItem(3978, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3978")]
+        public async Task TestLocalFunctionAttributeListAsync()
+        {
+            var testCode = @"using System;
+
+class TestClass
+{
+    void Outer()
+    {
+        [Attr1, {|#0:Attr2|}]
+        void Local()
+        {
+        }
+    }
+}
+
+[AttributeUsage(AttributeTargets.All, AllowMultiple = true)]
+class Attr1Attribute : Attribute
+{
+}
+
+[AttributeUsage(AttributeTargets.All, AllowMultiple = true)]
+class Attr2Attribute : Attribute
+{
+}
+";
+
+            var fixedCode = @"using System;
+
+class TestClass
+{
+    void Outer()
+    {
+        [Attr1]
+        [Attr2]
+        void Local()
+        {
+        }
+    }
+}
+
+[AttributeUsage(AttributeTargets.All, AllowMultiple = true)]
+class Attr1Attribute : Attribute
+{
+}
+
+[AttributeUsage(AttributeTargets.All, AllowMultiple = true)]
+class Attr2Attribute : Attribute
+{
+}
+";
+
+            await VerifyCSharpFixAsync(testCode, Diagnostic().WithLocation(0), fixedCode, CancellationToken.None).ConfigureAwait(false);
+        }
     }
 }