How can I tell compiler to copy wwwroot from one project to Tests proj?

In your Tests.csproj you could set up a link to your wwwroot folder:

<ItemGroup>
  <Content Include="..\AppRunner\wwwroot\**" Link="wwwroot\%(RecursiveDir)%(Filename)%(Extension)" CopyToOutputDirectory="Always" />
</ItemGroup>

In Visual Studio this will look like a regular wwwroot folder in your Tests project, but it is actually just a link to the folder in AppRunner. When you specify CopyToOutputDirectory this folder and its contents will be copied to the bin folder when you build the Tests project