Update SA1001 tests for function pointers

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/SpacingRules/SA1001CSharp9UnitTests.cs

@@ -3,9 +3,43 @@
 
 namespace StyleCop.Analyzers.Test.CSharp9.SpacingRules
 {
+    using System.Threading;
+    using System.Threading.Tasks;
     using StyleCop.Analyzers.Test.CSharp8.SpacingRules;
+    using Xunit;
+
+    using static StyleCop.Analyzers.Test.Verifiers.StyleCopCodeFixVerifier<
+        StyleCop.Analyzers.SpacingRules.SA1001CommasMustBeSpacedCorrectly,
+        StyleCop.Analyzers.SpacingRules.TokenSpacingCodeFixProvider>;
 
     public partial class SA1001CSharp9UnitTests : SA1001CSharp8UnitTests
     {
+        [Fact]
+        [WorkItem(3970, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3970")]
+        public async Task TestFunctionPointerParameterSpacingAsync()
+        {
+            var testCode = @"public class TestClass
+{
+    private unsafe delegate*<int{|#0:,|}int, void> field1;
+    private unsafe delegate*<int {|#1:,|}int, void> field2;
+}
+";
+
+            var fixedCode = @"public class TestClass
+{
+    private unsafe delegate*<int, int, void> field1;
+    private unsafe delegate*<int, int, void> field2;
+}
+";
+
+            var expected = new[]
+            {
+                Diagnostic().WithLocation(0).WithArguments(string.Empty, "followed"),
+                Diagnostic().WithLocation(1).WithArguments(" not", "preceded"),
+                Diagnostic().WithLocation(1).WithArguments(string.Empty, "followed"),
+            };
+
+            await VerifyCSharpFixAsync(testCode, expected, fixedCode, CancellationToken.None).ConfigureAwait(false);
+        }
     }
 }