Testing Elixir: assert_receive throws "no matching message" error (page 85, B6.0)

First iteration that uses Process.sleep/1 works but the stab on using assert_receive doesn’t. I’ve even increased the timeout to 5,000 milliseconds for assert_receive but the test still fails with “no matching message”.

I can’t figure out what’s wrong with the test (for now). By the way, I’m using Mox 1.0 and Elixir 1.11.4.

If I’ve figured out, I’ll report back.