Downgarade net 3.1

Listen/Listen.sln

+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.3.32901.215
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Listen", "Listen\Listen.csproj", "{9A2F19F8-B41B-4A4C-8AF7-5CEBABE61C68}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Listen_UnitTest", "Listen_UnitTest\Listen_UnitTest.csproj", "{15B7B485-625D-41C7-B5E5-1EC366033211}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{9A2F19F8-B41B-4A4C-8AF7-5CEBABE61C68}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{9A2F19F8-B41B-4A4C-8AF7-5CEBABE61C68}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{9A2F19F8-B41B-4A4C-8AF7-5CEBABE61C68}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{9A2F19F8-B41B-4A4C-8AF7-5CEBABE61C68}.Release|Any CPU.Build.0 = Release|Any CPU
+		{15B7B485-625D-41C7-B5E5-1EC366033211}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{15B7B485-625D-41C7-B5E5-1EC366033211}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{15B7B485-625D-41C7-B5E5-1EC366033211}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{15B7B485-625D-41C7-B5E5-1EC366033211}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {A4AB9627-02E9-44A7-BAD8-5D408616DA67}
+	EndGlobalSection
+EndGlobal

Listen/Listen/Listen.csproj

+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
+  </PropertyGroup>
+
+</Project>

Listen/Listen/Program.cs

+using System;
+using System.Collections.Generic;
+
+namespace Listen
+{
+    public class ListClass
+    {
+        static void Main(string[] args)
+        {
+            ListClass prg = new ListClass();
+            prg.getList();
+
+        }
+
+        public List<string> getList()
+        {
+            //Ergänzen sie Hier ihren Code
+
+
+            return;
+        }
+
+
+
+    }
+}

Listen/Listen_UnitTest/Listen_UnitTest.csproj

+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
+
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
+    <PackageReference Include="MSTest.TestAdapter" Version="2.2.8" />
+    <PackageReference Include="MSTest.TestFramework" Version="2.2.8" />
+    <PackageReference Include="coverlet.collector" Version="3.1.2" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Listen\Listen.csproj" />
+  </ItemGroup>
+
+</Project>

Listen/Listen_UnitTest/UnitTest1.cs

+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Listen;
+using Microsoft.VisualStudio.TestPlatform.TestHost;
+using System.Collections.Generic;
+
+namespace Listen_UnitTest
+{
+    [TestClass]
+    public class UnitTest1
+    {
+        [TestMethod]
+        public void TestMethod1()
+        {
+            //Arrange
+            ListClass list = new ListClass();
+
+            //Act
+            List<string> result = list.getList();
+
+
+            List<string> Studenten = new List<string>();
+            Studenten.Add("Daniel");
+            Studenten.Add("Tim");
+            Studenten.Add("Peter");
+
+            //Assert
+            CollectionAssert.AreEqual(result, Studenten);
+        }
+
+    }
+}