diff --git a/.appveyor.yml b/.appveyor.yml
index ebb64c6..d86285f 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -2,11 +2,10 @@ version: '{build}'
 skip_branch_with_pr: true
 image: Visual Studio 2017
 install:
-  - ps: nuget install OpenCover -OutputDirectory packages -Version 4.7.922
   - ps: dotnet tool install coveralls.net --tool-path tools
 build_script:  
   - cmd: dotnet build src/Castle.Sdk -c Release -f netstandard2.0
   - cmd: dotnet build src/Castle.Sdk -c Release -f net461
-test_script:  
-  - ps: .\packages\OpenCover.4.7.922\tools\OpenCover.Console.exe -register:user -target:dotnet.exe -targetargs:"test src/Tests/Tests.csproj" -filter:"+[Castle.Sdk*]*" -oldStyle -output:opencoverCoverage.xml
-  - ps: .\tools\csmacnz.coveralls.exe --opencover -i opencoverCoverage.xml --useRelativePaths --repoToken $env:COVERALLS_REPO_TOKEN --commitId $env:APPVEYOR_REPO_COMMIT --commitBranch $env:APPVEYOR_REPO_BRANCH --commitAuthor $env:APPVEYOR_REPO_COMMIT_AUTHOR --commitEmail $env:APPVEYOR_REPO_COMMIT_AUTHOR_EMAIL --commitMessage $env:APPVEYOR_REPO_COMMIT_MESSAGE --jobId $env:APPVEYOR_JOB_ID
+test_script:    
+  - ps: dotnet test /p:CollectCoverage=true /p:CoverletOutputFormat=opencover /p:Include="[Castle.Sdk*]*" src/Tests/Tests.csproj
+  - ps: .\tools\csmacnz.coveralls.exe --opencover -i src/Tests/coverage.opencover.xml --useRelativePaths --repoToken $env:COVERALLS_REPO_TOKEN --commitId $env:APPVEYOR_REPO_COMMIT --commitBranch $env:APPVEYOR_REPO_BRANCH --commitAuthor $env:APPVEYOR_REPO_COMMIT_AUTHOR --commitEmail $env:APPVEYOR_REPO_COMMIT_AUTHOR_EMAIL --commitMessage $env:APPVEYOR_REPO_COMMIT_MESSAGE --jobId $env:APPVEYOR_JOB_ID  
diff --git a/src/Tests/When_converting_http_messages.cs b/src/Tests/Sending/When_converting_http_messages.cs
similarity index 97%
rename from src/Tests/When_converting_http_messages.cs
rename to src/Tests/Sending/When_converting_http_messages.cs
index 6d11797..c458945 100644
--- a/src/Tests/When_converting_http_messages.cs
+++ b/src/Tests/Sending/When_converting_http_messages.cs
@@ -6,7 +6,7 @@
 using Tests.SetUp;
 using Xunit;
 
-namespace Tests
+namespace Tests.Sending
 {
     public class When_converting_http_messages
     {
diff --git a/src/Tests/When_creating_message_sender.cs b/src/Tests/Sending/When_creating_message_sender.cs
similarity index 97%
rename from src/Tests/When_creating_message_sender.cs
rename to src/Tests/Sending/When_creating_message_sender.cs
index 706b02a..182eb68 100644
--- a/src/Tests/When_creating_message_sender.cs
+++ b/src/Tests/Sending/When_creating_message_sender.cs
@@ -5,7 +5,7 @@
 using Tests.SetUp;
 using Xunit;
 
-namespace Tests
+namespace Tests.Sending
 {
     public class When_creating_message_sender
     {
diff --git a/src/Tests/When_sending_requests.cs b/src/Tests/Sending/When_sending_requests.cs
similarity index 99%
rename from src/Tests/When_sending_requests.cs
rename to src/Tests/Sending/When_sending_requests.cs
index 88c7409..2351345 100644
--- a/src/Tests/When_sending_requests.cs
+++ b/src/Tests/Sending/When_sending_requests.cs
@@ -10,7 +10,7 @@
 using Tests.SetUp;
 using Xunit;
 
-namespace Tests
+namespace Tests.Sending
 {
     public class When_sending_requests
     {
diff --git a/src/Tests/When_sending_with_no_track.cs b/src/Tests/Sending/When_sending_with_no_track.cs
similarity index 98%
rename from src/Tests/When_sending_with_no_track.cs
rename to src/Tests/Sending/When_sending_with_no_track.cs
index 03cc4ef..d989b1d 100644
--- a/src/Tests/When_sending_with_no_track.cs
+++ b/src/Tests/Sending/When_sending_with_no_track.cs
@@ -4,7 +4,7 @@
 using FluentAssertions;
 using Xunit;
 
-namespace Tests
+namespace Tests.Sending
 {
     public class When_sending_with_no_track
     {
diff --git a/src/Tests/Tests.csproj b/src/Tests/Tests.csproj
index c9176fd..4d59bfc 100644
--- a/src/Tests/Tests.csproj
+++ b/src/Tests/Tests.csproj
@@ -10,7 +10,7 @@
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
-    <DebugType>full</DebugType>
+    <DebugType>portable</DebugType>
     <DebugSymbols>true</DebugSymbols>
   </PropertyGroup>
 
@@ -18,6 +18,10 @@
     <PackageReference Include="AutoFixture" Version="4.8.0" />
     <PackageReference Include="AutoFixture.AutoNSubstitute" Version="4.8.0" />
     <PackageReference Include="AutoFixture.Xunit2" Version="4.8.0" />
+    <PackageReference Include="coverlet.msbuild" Version="2.6.0">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
+    </PackageReference>
     <PackageReference Include="FluentAssertions" Version="5.6.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.9.0" />
     <PackageReference Include="NSubstitute" Version="4.0.0" />
diff --git a/src/Tests/When_creating_configuration.cs b/src/Tests/When_creating_configuration.cs
index b7c76b2..e586094 100644
--- a/src/Tests/When_creating_configuration.cs
+++ b/src/Tests/When_creating_configuration.cs
@@ -15,6 +15,14 @@ public void Should_always_add_Cookie_when_setting_blacklist(CastleConfiguration
             configuration.Blacklist.Should().Contain("Cookie");
         }
 
+        [Theory, AutoFakeData]
+        public void Should_preserve_Cookie_when_setting_blacklist_to_null(CastleConfiguration configuration)
+        {
+            configuration.Blacklist = null;
+
+            configuration.Blacklist.Should().Contain("Cookie");
+        }
+
         [Fact]
         public void Should_be_able_to_get_recommended_whitelist()
         {