JUst one target

appveyor.yml

@@ -1,5 +1,5 @@
 version: '{build}'
-image: Visual Studio 2017
+image: Visual Studio 2019
 
 pull_requests:
   do_not_increment_build_number: true

build.cake

@@ -49,12 +49,9 @@ Task("Test")
         var settings = new DotNetCoreTestSettings
         {
             Configuration = "Release",
-            Framework = "netcoreapp2.2"
+            Framework = "netcoreapp3.1"
         };
         DotNetCoreTest(file.ToString(), settings);
-       
-        settings.Framework = "netcoreapp3.1";
-        DotNetCoreTest(file.ToString(), settings);
     }
 });
 
@@ -67,7 +64,7 @@ Task("Pack")
         MSBuild("src/SharpCompress/SharpCompress.csproj", c => c
             .SetConfiguration("Release")
             .SetVerbosity(Verbosity.Minimal)
-            .UseToolVersion(MSBuildToolVersion.VS2017)
+            .UseToolVersion(MSBuildToolVersion.VS2019)
             .WithProperty("NoBuild", "true")
             .WithTarget("Pack"));
     } 

tests/SharpCompress.Test/SharpCompress.Test.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netcoreapp2.2;netcoreapp3.1</TargetFrameworks>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
     <AssemblyName>SharpCompress.Test</AssemblyName>
     <AssemblyOriginatorKeyFile>../../SharpCompress.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>