Patch:
- https://github.com/ihumanable/patch
- https://hexdocs.pm/patch/readme.html
- https://discord.com/blog/why-and-how-discord-uses-patch-to-test-elixir

Mimic
- https://hex.pm/packages/mimic

Mockery
- https://github.com/appunite/mockery


Dependency Injection:


DefInject
- https://github.com/jechol/definject
- Unobtrusive Dependency Injector for Elixir


Rewire
- Dependency injection for Elixir. Zero code changes required.
- https://hex.pm/packages/rewire
- How does it deal with nested modules?
    - Only the dependencies of the rewired module will be replaced.
    - Any modules defined around the rewired module will be ignored.
    - All references of the rewired module to them will be pointing to the original.
    - You're always able to rewire them separately yourself.

Resolve
- https://github.com/amclain/resolve


Injector - Simple dependency injection for Elixir. Suitable to use with Mox.
- https://github.com/farhadi/injector


Hook - A runtime resolution library. Useful for dependency injection and mocks.
- https://hex.pm/packages/hook