andresnator Dependency Seam Detection
Find hard-to-control dependencies and propose seams that make tests possible before refactor.
Dependency smells
newinside business logic.- Static calls and singletons.
- System clock, random, filesystem, environment, or global config.
- Direct DB access, external services, queues, event buses, cache, threading, or async work.
Seam options
- Constructor injection.
- Interface seam.
- Object seam.
- Wrapper or adapter.
- Parameter injection.
- Protected method seam.
- Sprout method.
- Sprout class.
Seams and enabling points
A seam is a place where behavior can be changed without editing the code at that place; every seam has an enabling point where the substitution is decided. Object seams (polymorphism, injection) are the default in OO code; link/classpath seams (test-time substitution of a dependency at the linker or classpath level) and preprocessing seams sit below them and matter when the code itself cannot be edited.
Selection rule
Prefer the least invasive technique that lets a test run: parameter or constructor injection before interface extraction, interface extraction before subclass-and-override, subclass-and-override before brute force. Dependency-breaking is medicine, not vitamins — a scar (a slightly awkward seam) is acceptable and gets cleaned up in a later refactor once tests exist.
References
references/dependency-breaking-catalog.md— dependency-breaking catalog (WELC): four strategies, the individual techniques with contraindications, and the instantiation-blocker table.