diff --git a/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/DocumentationRules/SA1611CSharp9UnitTests.cs b/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/DocumentationRules/SA1611CSharp9UnitTests.cs
index 004f297bd..3bed2e128 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/DocumentationRules/SA1611CSharp9UnitTests.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/DocumentationRules/SA1611CSharp9UnitTests.cs
@@ -37,5 +37,24 @@ public async Task TestPrimaryRecordConstructorIncludeMissingParametersAsync(stri
 
             await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
         }
+
+        [Fact]
+        [WorkItem(3977, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3977")]
+        public async Task TestLambdaDiscardParametersAsync()
+        {
+            var testCode = @"
+/// <summary>Test class.</summary>
+public class TestClass
+{
+    /// <summary>Test method.</summary>
+    public void TestMethod()
+    {
+        System.Func<int, int, int> handler = (_, _) => 0;
+    }
+}
+";
+
+            await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+        }
     }
 }
diff --git a/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/DocumentationRules/SA1612CSharp9UnitTests.cs b/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/DocumentationRules/SA1612CSharp9UnitTests.cs
index 19d9c78db..3beab799b 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/DocumentationRules/SA1612CSharp9UnitTests.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/DocumentationRules/SA1612CSharp9UnitTests.cs
@@ -3,9 +3,31 @@
 
 namespace StyleCop.Analyzers.Test.CSharp9.DocumentationRules
 {
+    using System.Threading;
+    using System.Threading.Tasks;
+    using Microsoft.CodeAnalysis.Testing;
     using StyleCop.Analyzers.Test.CSharp8.DocumentationRules;
+    using Xunit;
 
     public partial class SA1612CSharp9UnitTests : SA1612CSharp8UnitTests
     {
+        [Fact]
+        [WorkItem(3977, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3977")]
+        public async Task TestLambdaDiscardParametersAsync()
+        {
+            var testCode = @"
+/// <summary>Test class.</summary>
+public class TestClass
+{
+    /// <summary>Test method.</summary>
+    public void TestMethod()
+    {
+        System.Func<int, int, int> handler = (_, _) => 0;
+    }
+}
+";
+
+            await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+        }
     }
 }
diff --git a/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/NamingRules/SA1312CSharp9UnitTests.cs b/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/NamingRules/SA1312CSharp9UnitTests.cs
index ab3ed34dd..e4ca713b2 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/NamingRules/SA1312CSharp9UnitTests.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/NamingRules/SA1312CSharp9UnitTests.cs
@@ -3,9 +3,34 @@
 
 namespace StyleCop.Analyzers.Test.CSharp9.NamingRules
 {
+    using System.Threading;
+    using System.Threading.Tasks;
+    using Microsoft.CodeAnalysis.Testing;
     using StyleCop.Analyzers.Test.CSharp8.NamingRules;
+    using Xunit;
+    using static StyleCop.Analyzers.Test.Verifiers.StyleCopCodeFixVerifier<
+        StyleCop.Analyzers.NamingRules.SA1312VariableNamesMustBeginWithLowerCaseLetter,
+        StyleCop.Analyzers.NamingRules.RenameToLowerCaseCodeFixProvider>;
 
     public partial class SA1312CSharp9UnitTests : SA1312CSharp8UnitTests
     {
+        [Fact]
+        [WorkItem(3977, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3977")]
+        public async Task TestLambdaDiscardParametersDoNotReportAsync()
+        {
+            var testCode = @"
+using System;
+
+public class TestClass
+{
+    public void Test()
+    {
+        Func<int, int, int> handler = (_, _) => 0;
+    }
+}
+";
+
+            await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+        }
     }
 }
diff --git a/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/NamingRules/SA1313CSharp9UnitTests.cs b/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/NamingRules/SA1313CSharp9UnitTests.cs
index bd393fb24..f095ea1a1 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/NamingRules/SA1313CSharp9UnitTests.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/NamingRules/SA1313CSharp9UnitTests.cs
@@ -14,6 +14,25 @@ namespace StyleCop.Analyzers.Test.CSharp9.NamingRules
 
     public partial class SA1313CSharp9UnitTests : SA1313CSharp8UnitTests
     {
+        [Fact]
+        [WorkItem(3977, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3977")]
+        public async Task TestLambdaDiscardParametersAsync()
+        {
+            var testCode = @"
+using System;
+
+public class TestClass
+{
+    public void Test()
+    {
+        Action<int, int> handler = (_, _) => { };
+    }
+}
+";
+
+            await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+        }
+
         [Fact]
         [WorkItem(3168, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3168")]
         [WorkItem(3181, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3181")]
diff --git a/StyleCop.Analyzers/StyleCop.Analyzers.Test/DocumentationRules/SA1612UnitTests.cs b/StyleCop.Analyzers/StyleCop.Analyzers.Test/DocumentationRules/SA1612UnitTests.cs
index 5c2728e8f..6c6fd303e 100644
--- a/StyleCop.Analyzers/StyleCop.Analyzers.Test/DocumentationRules/SA1612UnitTests.cs
+++ b/StyleCop.Analyzers/StyleCop.Analyzers.Test/DocumentationRules/SA1612UnitTests.cs
@@ -1,8 +1,6 @@
 // Copyright (c) Tunnel Vision Laboratories, LLC. All Rights Reserved.
 // Licensed under the MIT License. See LICENSE in the project root for license information.
 
-#nullable disable
-
 namespace StyleCop.Analyzers.Test.DocumentationRules
 {
     using System.Collections.Generic;
@@ -562,35 +560,13 @@ public class ClassName
             await VerifyCSharpDiagnosticAsync(testCode, DiagnosticResult.EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
         }
 
-        private static DiagnosticResult[] GetExpectedDiagnostics(DiagnosticResult normallyExpected, string declaration)
-        {
-            return GetExpectedDiagnostics(new[] { normallyExpected }, declaration);
-        }
-
-        // Syntax node actions for type declarations with a primary constructor were called twice
-        // before support for c# 11 was added.
-        private static DiagnosticResult[] GetExpectedDiagnostics(DiagnosticResult[] normallyExpected, string declaration)
-        {
-            var isPrimaryConstructor = declaration.Contains("record") || declaration.Contains("class") || declaration.Contains("struct");
-
-            if (isPrimaryConstructor && !LightupHelpers.SupportsCSharp11)
-            {
-                // Diagnostic issued twice because of https://github.com/dotnet/roslyn/issues/53136 and https://github.com/dotnet/roslyn/issues/70488
-                return normallyExpected.Concat(normallyExpected).ToArray();
-            }
-            else
-            {
-                return normallyExpected;
-            }
-        }
-
-        private static Task VerifyCSharpDiagnosticAsync(string source, DiagnosticResult[] expected, CancellationToken cancellationToken)
+        protected static Task VerifyCSharpDiagnosticAsync(string source, DiagnosticResult[] expected, CancellationToken cancellationToken)
             => VerifyCSharpDiagnosticAsync(source, testSettings: null, expected, ignoreCompilerDiagnostics: false, cancellationToken);
 
-        private static Task VerifyCSharpDiagnosticAsync(string source, string testSettings, DiagnosticResult[] expected, CancellationToken cancellationToken)
+        protected static Task VerifyCSharpDiagnosticAsync(string source, string? testSettings, DiagnosticResult[] expected, CancellationToken cancellationToken)
             => VerifyCSharpDiagnosticAsync(source, testSettings, expected, ignoreCompilerDiagnostics: false, cancellationToken);
 
-        private static Task VerifyCSharpDiagnosticAsync(string source, string testSettings, DiagnosticResult[] expected, bool ignoreCompilerDiagnostics, CancellationToken cancellationToken)
+        protected static Task VerifyCSharpDiagnosticAsync(string source, string? testSettings, DiagnosticResult[] expected, bool ignoreCompilerDiagnostics, CancellationToken cancellationToken)
         {
             string contentWithoutParamDocumentation = @"<?xml version=""1.0"" encoding=""utf-8"" ?>
 <ClassName>
@@ -696,5 +672,27 @@ private static Task VerifyCSharpDiagnosticAsync(string source, string testSettin
             test.ExpectedDiagnostics.AddRange(expected);
             return test.RunAsync(cancellationToken);
         }
+
+        private static DiagnosticResult[] GetExpectedDiagnostics(DiagnosticResult normallyExpected, string declaration)
+        {
+            return GetExpectedDiagnostics(new[] { normallyExpected }, declaration);
+        }
+
+        // Syntax node actions for type declarations with a primary constructor were called twice
+        // before support for c# 11 was added.
+        private static DiagnosticResult[] GetExpectedDiagnostics(DiagnosticResult[] normallyExpected, string declaration)
+        {
+            var isPrimaryConstructor = declaration.Contains("record") || declaration.Contains("class") || declaration.Contains("struct");
+
+            if (isPrimaryConstructor && !LightupHelpers.SupportsCSharp11)
+            {
+                // Diagnostic issued twice because of https://github.com/dotnet/roslyn/issues/53136 and https://github.com/dotnet/roslyn/issues/70488
+                return normallyExpected.Concat(normallyExpected).ToArray();
+            }
+            else
+            {
+                return normallyExpected;
+            }
+        }
     }
 }