title: xUnit tests not found when running in docker container
body: <p>I am making a Dockerfile for a dotnet core project with some xUnit tests. I want to run the unit tests when the images are being built. However when I docker build I get the following message at the test step:</p>
  
  <blockquote>
    <p>No test is available in /ciad/tests/bin/Debug/netcoreapp2.1/Tests.dll. Make sure that test discoverer &amp; executors are registered and platform &amp; framework version settings are appropriate and try again.</p>
  </blockquote>
  
  <p>Here is the Dockerfile:</p>
  
  <pre><code>FROM microsoft/dotnet:2.1-aspnetcore-runtime AS base
  FROM microsoft/dotnet:2.1-sdk AS build
  
  WORKDIR /ciad
  
  # restore
  COPY API/API.csproj ./api/
  RUN dotnet restore api/API.csproj
  COPY Tests/Tests.csproj ./tests/
  RUN dotnet restore tests/Tests.csproj
  
  # copy src
  COPY . .
  
  # test
  RUN dotnet test tests/Tests.csproj
  </code></pre>
  
  <p>I'm aware that this is an incomplete dockerfile. I'm just stuck with the tests at the moment. Could anyone see what I'm missing?</p>
  
  <p>Good to mention that tests run fine in VS and "dotnet test" command works too. I can also see that the Tests projects' files are copied to the container. 
  I run:</p>
  
  <pre><code>docker build -t testing .
  </code></pre>