diff --git a/MoreLinq.Test/AggregateTest.cs b/MoreLinq.Test/AggregateTest.cs
index 98b49e8b6..81ee2b5de 100644
--- a/MoreLinq.Test/AggregateTest.cs
+++ b/MoreLinq.Test/AggregateTest.cs
@@ -28,6 +28,8 @@ namespace MoreLinq.Test
     using NUnit.Framework.Interfaces;
     using static FuncModule;
 
+    using static MoreLinq.Extensions.AppendExtension;
+
     [TestFixture]
     public class AggregateTest
     {
diff --git a/MoreLinq.Test/AppendTest.cs b/MoreLinq.Test/AppendTest.cs
index df46b13c7..e3c6ac962 100644
--- a/MoreLinq.Test/AppendTest.cs
+++ b/MoreLinq.Test/AppendTest.cs
@@ -20,6 +20,8 @@ namespace MoreLinq.Test
     using System.Collections.Generic;
     using NUnit.Framework;
 
+    using static MoreLinq.Extensions.AppendExtension;
+
     [TestFixture]
     public class AppendTest
     {
diff --git a/MoreLinq.Test/MoreLinq.Test.csproj b/MoreLinq.Test/MoreLinq.Test.csproj
index 45f75013c..7a8de5097 100644
--- a/MoreLinq.Test/MoreLinq.Test.csproj
+++ b/MoreLinq.Test/MoreLinq.Test.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <AssemblyTitle>MoreLinq.Test</AssemblyTitle>
-    <TargetFrameworks>netcoreapp3.1;netcoreapp2.1;net451</TargetFrameworks>
+    <TargetFrameworks>netcoreapp2.1;netcoreapp3.0;netcoreapp3.1;net451;net471;net48</TargetFrameworks>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
     <DebugType>portable</DebugType>
     <AssemblyName>MoreLinq.Test</AssemblyName>
@@ -69,7 +69,7 @@
       <Compile Include="WatchableEnumerator.cs" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net451' ">
+  <ItemGroup Condition=" '$(TargetFramework)' == 'net451' or '$(TargetFramework)' == 'net471' or '$(TargetFramework)' == 'net48' ">
     <Reference Include="System" />
     <Reference Include="System.Data.DataSetExtensions" />
     <Reference Include="System.Data" />
diff --git a/MoreLinq.Test/PartialSortTest.cs b/MoreLinq.Test/PartialSortTest.cs
index 04257a737..fd8431ab6 100644
--- a/MoreLinq.Test/PartialSortTest.cs
+++ b/MoreLinq.Test/PartialSortTest.cs
@@ -20,6 +20,8 @@ namespace MoreLinq.Test
     using System;
     using NUnit.Framework;
 
+    using static MoreLinq.Extensions.AppendExtension;
+
     [TestFixture]
     public class PartialSortTests
     {
diff --git a/MoreLinq.Test/PrependTest.cs b/MoreLinq.Test/PrependTest.cs
index 381e1deba..e28bb48a8 100644
--- a/MoreLinq.Test/PrependTest.cs
+++ b/MoreLinq.Test/PrependTest.cs
@@ -21,6 +21,8 @@ namespace MoreLinq.Test
     using NUnit.Framework;
     using NUnit.Framework.Interfaces;
 
+    using static MoreLinq.Extensions.PrependExtension;
+
     [TestFixture]
     public class PrependTest
     {
diff --git a/MoreLinq.Test/SkipLastTest.cs b/MoreLinq.Test/SkipLastTest.cs
index 715f53be4..e6be94faa 100644
--- a/MoreLinq.Test/SkipLastTest.cs
+++ b/MoreLinq.Test/SkipLastTest.cs
@@ -19,6 +19,8 @@ namespace MoreLinq.Test
 {
     using NUnit.Framework;
 
+    using static MoreLinq.Extensions.SkipLastExtension;
+
     [TestFixture]
     public class SkipLastTest
     {
diff --git a/MoreLinq.Test/TakeLastTest.cs b/MoreLinq.Test/TakeLastTest.cs
index 16c23e633..96674a000 100644
--- a/MoreLinq.Test/TakeLastTest.cs
+++ b/MoreLinq.Test/TakeLastTest.cs
@@ -17,9 +17,11 @@
 
 namespace MoreLinq.Test
 {
-    using NUnit.Framework;
-    using System.Collections.Generic;
     using System;
+    using System.Collections.Generic;
+    using NUnit.Framework;
+
+    using static MoreLinq.Extensions.TakeLastExtension;
 
     [TestFixture]
     public class TakeLastTest