Boundaries
summary
Argues that converting boundaries to functional core (pure functions returning values) plus an imperative shell (IO, DB, networks) removes fragile mocks, makes unit tests fast, and avoids boundary breaks; demonstrates a ~600-line Twitter client with a 153-line shell and a 35-line actor library but zero shell tests; points out path explosion (2^n, e.g. 500 conditionals → ~150-digit space), shows the value-based design easily parallelizes the sweeper into three cores, and warns about allocation costs on MRI versus actor-friendly VMs.
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chapters (14)
- 0:00Intro
- 0:40Test doubles
- 6:34Why integration tests dont work
- 8:00Values
- 10:57Procedural vs Functional
- 14:07Reintroducing State
- 17:15Actor Model
- 18:30Boundary between components
- 21:41Testing
- 22:25Comments Questions
- 30:26Functional Example
- 32:00Cursor
- 33:04Cursor Manipulation
- 39:35Database clearing
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