diff --git a/analyzers/tests/SonarAnalyzer.UnitTest/Rules/RedundantDeclarationTest.cs b/analyzers/tests/SonarAnalyzer.UnitTest/Rules/RedundantDeclarationTest.cs
index 22676105017..80a749b1f87 100644
--- a/analyzers/tests/SonarAnalyzer.UnitTest/Rules/RedundantDeclarationTest.cs
+++ b/analyzers/tests/SonarAnalyzer.UnitTest/Rules/RedundantDeclarationTest.cs
@@ -70,6 +70,30 @@ public void RedundantDeclaration_CSharp10_CodeFix_ExplicitDelegate() =>
                 .WithOptions(ParseOptionsHelper.FromCSharp10)
                 .VerifyCodeFix();
 
+        [TestMethod]
+        public void RedundantDeclaration_CSharp12() =>
+            builder.AddPaths("RedundantDeclaration.CSharp12.cs")
+                .WithOptions(ParseOptionsHelper.FromCSharp12)
+                .Verify();
+
+        [TestMethod]
+        public void RedundantDeclaration_CSharp12_CodeFix_ArraySize() =>
+            codeFixBuilder.AddPaths("RedundantDeclaration.CSharp12.cs")
+                .WithCodeFix<RedundantDeclarationCodeFix>()
+                .WithCodeFixTitle(RedundantDeclarationCodeFix.TitleRedundantArraySize)
+                .WithCodeFixedPaths("RedundantDeclaration.CSharp12.ArraySize.Fixed.cs")
+                .WithOptions(ParseOptionsHelper.FromCSharp12)
+                .VerifyCodeFix();
+
+        [TestMethod]
+        public void RedundantDeclaration_CSharp12_CodeFix_LambdaParameterType() =>
+            codeFixBuilder.AddPaths("RedundantDeclaration.CSharp12.cs")
+                .WithCodeFix<RedundantDeclarationCodeFix>()
+                .WithCodeFixTitle(RedundantDeclarationCodeFix.TitleRedundantLambdaParameterType)
+                .WithCodeFixedPaths("RedundantDeclaration.CSharp12.LambdaParameterType.Fixed.cs")
+                .WithOptions(ParseOptionsHelper.FromCSharp12)
+                .VerifyCodeFix();
+
 #endif
 
         [TestMethod]
diff --git a/analyzers/tests/SonarAnalyzer.UnitTest/TestCases/RedundantDeclaration.CSharp12.ArraySize.Fixed.cs b/analyzers/tests/SonarAnalyzer.UnitTest/TestCases/RedundantDeclaration.CSharp12.ArraySize.Fixed.cs
new file mode 100644
index 00000000000..c4168356fac
--- /dev/null
+++ b/analyzers/tests/SonarAnalyzer.UnitTest/TestCases/RedundantDeclaration.CSharp12.ArraySize.Fixed.cs
@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+
+namespace AliasAnyType
+{
+    using Int = int;
+    using IntArray = int[];
+    using IntNullable = int?;
+    using Point = (int x, int y);
+    using ThreeInts = int[3];                   // Error [CS0270]: Array size cannot be specified in a variable declaration
+    using IntToIntFunc = Func<int, int>;
+
+    class AClass
+    {
+        void AliasWithArraySize()
+        {
+            IntArray a1 = new Int[] { 1, 2, 3 };  // Fixed
+        }
+
+        void AliasWithUnnecessaryType()
+        {
+            IntToIntFunc f = (Int i) => i;      // Fixed
+        }
+
+        void AliasWithInitializer()
+        {
+            IntArray a1 = new IntArray { };     // Error [CS8386]: Invalid object creation
+            var a2 = new IntArray { };          // Error [CS8386]: Invalid object creation
+            int[] a3 = new IntArray();          // Error [CS8386]: Invalid object creation
+        }
+
+        void AliasWithEmptyParamsList()
+        {
+            IntArray a1 = new IntArray();       // Error [CS8386]: Invalid object creation
+            var a2 = new IntArray();            // Error [CS8386]: Invalid object creation
+            int[] a3 = new IntArray();          // Error [CS8386]: Invalid object creation
+        }
+    }
+}
diff --git a/analyzers/tests/SonarAnalyzer.UnitTest/TestCases/RedundantDeclaration.CSharp12.LambdaParameterType.Fixed.cs b/analyzers/tests/SonarAnalyzer.UnitTest/TestCases/RedundantDeclaration.CSharp12.LambdaParameterType.Fixed.cs
new file mode 100644
index 00000000000..879f8e8f346
--- /dev/null
+++ b/analyzers/tests/SonarAnalyzer.UnitTest/TestCases/RedundantDeclaration.CSharp12.LambdaParameterType.Fixed.cs
@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+
+namespace AliasAnyType
+{
+    using Int = int;
+    using IntArray = int[];
+    using IntNullable = int?;
+    using Point = (int x, int y);
+    using ThreeInts = int[3];                   // Error [CS0270]: Array size cannot be specified in a variable declaration
+    using IntToIntFunc = Func<int, int>;
+
+    class AClass
+    {
+        void AliasWithArraySize()
+        {
+            IntArray a1 = new Int[3] { 1, 2, 3 };  // Fixed
+        }
+
+        void AliasWithUnnecessaryType()
+        {
+            IntToIntFunc f = (i) => i;      // Fixed
+        }
+
+        void AliasWithInitializer()
+        {
+            IntArray a1 = new IntArray { };     // Error [CS8386]: Invalid object creation
+            var a2 = new IntArray { };          // Error [CS8386]: Invalid object creation
+            int[] a3 = new IntArray();          // Error [CS8386]: Invalid object creation
+        }
+
+        void AliasWithEmptyParamsList()
+        {
+            IntArray a1 = new IntArray();       // Error [CS8386]: Invalid object creation
+            var a2 = new IntArray();            // Error [CS8386]: Invalid object creation
+            int[] a3 = new IntArray();          // Error [CS8386]: Invalid object creation
+        }
+    }
+}
diff --git a/analyzers/tests/SonarAnalyzer.UnitTest/TestCases/RedundantDeclaration.CSharp12.cs b/analyzers/tests/SonarAnalyzer.UnitTest/TestCases/RedundantDeclaration.CSharp12.cs
new file mode 100644
index 00000000000..9be1211a743
--- /dev/null
+++ b/analyzers/tests/SonarAnalyzer.UnitTest/TestCases/RedundantDeclaration.CSharp12.cs
@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+
+namespace AliasAnyType
+{
+    using Int = int;
+    using IntArray = int[];
+    using IntNullable = int?;
+    using Point = (int x, int y);
+    using ThreeInts = int[3];                   // Error [CS0270]: Array size cannot be specified in a variable declaration
+    using IntToIntFunc = Func<int, int>;
+
+    class AClass
+    {
+        void AliasWithArraySize()
+        {
+            IntArray a1 = new Int[3] { 1, 2, 3 };  // Noncompliant
+        }
+
+        void AliasWithUnnecessaryType()
+        {
+            IntToIntFunc f = (Int i) => i;      // Noncompliant {{Remove the type specification; it is redundant.}}
+        }
+
+        void AliasWithInitializer()
+        {
+            IntArray a1 = new IntArray { };     // Error [CS8386]: Invalid object creation
+            var a2 = new IntArray { };          // Error [CS8386]: Invalid object creation
+            int[] a3 = new IntArray();          // Error [CS8386]: Invalid object creation
+        }
+
+        void AliasWithEmptyParamsList()
+        {
+            IntArray a1 = new IntArray();       // Error [CS8386]: Invalid object creation
+            var a2 = new IntArray();            // Error [CS8386]: Invalid object creation
+            int[] a3 = new IntArray();          // Error [CS8386]: Invalid object creation
+        }
+    }
+}