seam
A place where behavior can be replaced without editing its consumer.
Use this when Tests need an alternative clock, storage system, or external service.
without the term
“I can't test this without hitting the real payment API and the real clock. Can you make it so I can swap those out for fake ones in tests without changing the code that uses them?”
with the term · How do you ask a model for seam?
Introduce a seam for this dependency. Run the consumer with the real implementation and a controlled test implementation.
What is seam?
A seam is a substitution point. Its location determines which behavior can vary independently.
Why does seam matter when vibe coding?
Hardwired dependencies make a small test require the entire environment.
How do you do seam?
Introduce the smallest useful substitution point. Check the same consumer with two implementations.
What goes wrong with seam?
Adding an interface everywhere creates indirection without useful substitution.