When developing, I like to have my tests in the same folder as the code and make the build process excluded test code for a production build (<Compile Remove=”**\*Test.cs” />).
So I created a .NET Core command line application in Visual Studio Code (my.command.line.csproj) and placed a test project file inside the samen folder (my.command.line.test.csproj).

my.command.line.csproj

<Project Sdk="Microsoft.NET.Sdk">

<PropertyGroup>

<OutputType>Exe</OutputType>

<TargetFramework>netcoreapp2.2</TargetFramework>

</PropertyGroup>

<ItemGroup>

 <Compile Remove="**\*Test.cs" />


</ItemGroup>

</Project>

my.command.line.test.csproj


<Project Sdk="Microsoft.NET.Sdk">

<PropertyGroup>

<TargetFramework>netcoreapp2.2</TargetFramework>

<IsPackable>false</IsPackable>

<GenerateProgramFile>false</GenerateProgramFile>

</PropertyGroup>

<ItemGroup>

<PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.9.0" />

<PackageReference Include="MSTest.TestAdapter" Version="1.3.2" />

<PackageReference Include="MSTest.TestFramework" Version="1.3.2" />

</ItemGroup>

</Project>

Then I executed dotnet test

This will throw the following error:
Program.cs(10,27): error CS0017: Program has more than one entry point defined. Compile with /main to specify the type that contains the entry point.

This can be fixed by adding: <GenerateProgramFile>false</GenerateProgramFile> to a PropertyGroup inside the my.command.line.test.csproj.

Then when you execute dotnet test again, you will get the error:

MSBUILD : error MSB1011: Specify which project or solution file to use because this folder contains more than one project or solution file.

To fix it, execute:
dotnet test “my.command.line.test.csproj”

When you execute dotnet watch test, you will first get the error

Multiple MSBuild project files found in ‘C:\Dev\’. Specify which to use with the –project option.

You might want to fix it like: dotnet watch –project “my.command.line.test.csproj” test, but then the watcher will start watching but you will get the error:

MSBUILD : error MSB1011: Specify which project or solution file to use because this folder contains more than one project or solution file.

watch : Exited with error code 1

watch : Waiting for a file to change before restarting dotnet…

To fix this, execute dotnet watch –project “my.command.line.test.csproj” test “my.command.line.test.csproj”

Now your tests will be executed and the tests will be re-executed, when any of the files change.