Question 1

How do I use Suture with Rails ActiveRecord?

Accepted Answer

Suture has built-in comparators for ActiveRecord that ignore created_at and updated_at by default. Configure custom excluded attributes in the comparator and set up seams in models or workers, as shown in the Rails app example in the README.

Question 2

Suture vs. traditional unit testing for refactoring?

Accepted Answer

Suture automates characterization tests based on recorded behavior, ideal for legacy code with unknown edge cases. Traditional unit tests require manual assertions and are better for new, well-understood code but less efficient for uncovering hidden behavior.

Question 3

Can Suture handle code that calls external APIs?

Accepted Answer

It's challenging because recordings depend on API responses at the time of recording. The README suggests narrowing seams to avoid external dependencies or using custom comparators, but side effects are a known limitation.

Question 4

How to record Suture calls in a production environment safely?

Accepted Answer

Set SUTURE_RECORD_CALLS=true in production, but ensure the sqlite database path is accessible and consider data privacy. Recordings can be fetched for verification in test environments, though this requires matching data states.

Question 5

What's the performance impact of using call_both mode?

Accepted Answer

call_both executes both old and new code paths, doubling execution time and resource usage. The README recommends using it only in staging environments, not in performance-critical production paths.

Question 6

How to write a custom comparator for complex objects in Suture?

Accepted Answer

Extend Suture::Comparator class and override the call method, or provide a lambda at create/verify call sites. Examples in the README show comparing specific attributes or using Marshal.dump for equivalence.

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