I believe they intentionally left it up to third party modules instead of baking in one way of doing it. I created a module called mock on their third party mod

I believe they intentionally left it up to third party modules instead of baking in one way of doing it. I created a module called mock on their third party module registry that can be used for spying on and stubbing functions. Even with third party modules, you cannot mock Deno.connect directly because the Deno object is not extensible. If you'd like to spy on or stub connect, you could have Deno.connect passed in to your function as an argument that you can replace in tests with a spy wrapper around it or your mocked out version of it.