title: Entity Framework Core InMemory database tests break when run in parallel
body: <p>When running all the test, I'm eventually getting errors saying: </p>
  
  <blockquote>
    <p>"An item with the same key has already been added. Key: 125"</p>
  </blockquote>
  
  <p>This doesn't happen when each test is run separately.</p>
  
  <p>The funny thing is that each test works with a different DbName, to avoid any conflict:</p>
  
  <pre><code>[TestMethod]
  public void Test1() 
  {
      using (var context = CreateTestingContext()) 
      {
          ...
      }
  }
  
  [TestMethod]
  public void Test2() 
  {
      using (var context = CreateTestingContext()) 
      {
          ...
      }
  }
  
  protected static SGDTPContext CreateTestingContext([CallerMemberName] string dbName = "TestingDb")
  {
      var builder = new DbContextOptionsBuilder&lt;MyDbContext&gt;().UseInMemoryDatabase(dbName);
      return new MyDbContext(builder.Options);
  }
  </code></pre>
  
  <p>It's really strange, because when I run the tests individually, they are Green! and when I run them all at the same time, some eventually fail.</p>
  
  <p>NOTE: I'm using the integrated MSTest from Visual Studio 2017.</p>