Ok, I’ve also looked deeper into this as well, and the issue here is in how you’re using test_helper.exs. Because you’re doing some compilation in there of what are essentially test fixtures, and (at the moment) Muzak doesn’t re-require test_helper.exs before each test run for each mutation, those test structs aren’t being re-compiled with each mutation. They’re only being compiled once with the un-mutated code.
This is because the types of things I’ve seen put in test_helper.exs are either things that only need to be done once and aren’t affected by any possible mutations (like configuring ExUnit), or things that aren’t idempotent (like inserting test fixtures into a DB) and so can’t be run multiple times. That’s also because I mainly used applications and not libraries as tests for Muzak, and libraries have way more macros and compile-time stuff going on usually.
This might end up being another necessary configuration option, but I do think this might end up being something that will be good to support. I’ll need to do a bit more research first and thinking to come up with a better way to handle this.
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