Question 1

How does Mneme compare to assert_value for Elixir snapshot testing?

Accepted Answer

Mneme integrates more seamlessly with ExUnit and offers interactive terminal prompts, while assert_value is another Elixir library with similar functionality but different workflows. Mneme's inspiration from tools like Insta and its focus on auto-updating with user confirmation might appeal to developers wanting a more guided experience.

Question 2

How to use Mneme in continuous integration without interactive prompts?

Accepted Answer

Set the CI environment variable to true (e.g., export CI=true), and Mneme will fail tests that would update instead of prompting. This ensures builds don't hang, but you'll need to manually update assertions locally before CI passes.

Question 3

Can Mneme handle complex data structures in auto-assertions?

Accepted Answer

Yes, Mneme generates patterns from any Elixir value, including complex data structures like maps or structs, using syntax-aware diffs. However, the generated patterns might be verbose, and you might need to tweak them for clarity in your tests.

Question 4

What happens if I reject an auto-update in Mneme?

Accepted Answer

If you reject a change, the test fails immediately, allowing you to inspect the mismatch. This maintains test integrity but requires manual intervention to fix the assertion or underlying code.

Question 5

Is Mneme suitable for large test suites with many async tests?

Accepted Answer

Mneme works with ExUnit's async tests since it integrates directly, but the interactive prompts might slow down runs if many assertions need updates. The built-in watcher (mix mneme.watch) can help with incremental feedback during development.

Question 6

How to revert an auto-update if I make a mistake with Mneme?

Accepted Answer

Since Mneme modifies source code, you should use version control (e.g., Git) to revert changes. There's no built-in undo feature, so careful review during prompts is recommended to avoid accidental updates.

Question 7

Does Mneme support customizing the diff output or assertion patterns?

Accepted Answer

The README doesn't mention customization options for diffs or patterns; it focuses on syntax-aware diffs and auto-generated patterns. For advanced needs, you might need to rely on ExUnit's existing assertion utilities or request features from the project.

mneme

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