How to avoid looking for tests in an assembly or project in Visual Studio 2019?

When I rebuild my C# project in Visual Studio 2019 and look at the "Tests" section on the Output window I see the following message:

[8/13/2019 9:58:08.397 AM Informational] ---------- Discovery started ----------
[8/13/2019 9:58:09.564 AM Warning] No test is available in H:\Foo\src\bin\Release\net461\Foo.dll. Make sure that test discoverer & executors are registered and platform & framework version settings are appropriate and try again.
[8/13/2019 9:58:09.612 AM Informational] ========== Discovery finished: 0 tests found (0:00:01.2086584) ==========

I have a separate project which contains my unit tests. Foo.dll will never contain tests. How can I avoid this assembly/project being scanned for tests and causing that warning message from being written?