Question 1

How do I set up Mox for testing in Elixir?

Accepted Answer

Define a behaviour, create a mock with Mox.defmock in test_helper.exs, configure your app to use the mock via Application.put_env, and use expect in tests with verify_on_exit! for cleanup. The README provides a basic usage example with WeatherBehaviour to guide you through the steps.

Question 2

What's the difference between Mox and Hammox?

Accepted Answer

Hammox is an enhanced version of Mox that automatically enforces behaviour typespecs, ensuring mock calls match the defined specifications. Mox focuses on concurrent mocking with behaviours, while Hammox adds type checking for more rigorous contract enforcement, as mentioned in the README's 'Enforcing consistency' section.

Question 3

Can Mox mock functions without behaviours?

Accepted Answer

No, Mox strictly requires mocks to be based on Elixir behaviours, enforcing explicit contracts. This means you cannot mock arbitrary functions ad-hoc, which can be a limitation if your codebase lacks behaviour definitions or needs dynamic mocking.

Question 4

How to verify function call counts with Mox?

Accepted Answer

Mox doesn't have built-in call count verification. You need to implement custom logic in your expect functions, such as using Elixir's Agent or stateful processes to track calls, or consider integrating with external tools like Hammox for additional checks.

Question 5

Best practices for using Mox with async tests in ExUnit?

Accepted Answer

Define mocks in test_helper.exs or setup_all blocks to avoid per-test module creation, use expect within individual tests to set return values, and ensure shared mocks are thread-safe. This allows concurrent test execution without overhead, as highlighted in the library's concurrency support feature.

mox

What is mox?

Overview

Use Cases

Best For

Related Projects

Found a gem we're missing?

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions