self-assertDesign objects that are fully responsible for their validity.
self-assert is a small TypeScript library for modeling valid domain objects
and assisting their creation through guided assistants (draft assistants).
This site is still a work in progress.
This library is inspired by the ideas of Hernán Wilkinson in his Diseño a la Gorra series, which explores software design as the craft of modeling real-world problems.
In that spirit, self-assert adopts a key principle:
A software system is a model of a specific problem domain—and
a good model is valid from the start, and teaches us how to use it.
This philosophy is reflected in two main ideas:
Assertions make objects responsible for enforcing their
own validity from the moment of creation.DraftAssistants help guide the construction of complete and
valid models, especially in interfaces with the external world
(like user input or APIs).Together, they support a design approach where validity is built in, not patched later.
And because validation rules live inside the domain model—not scattered across UI forms, API controllers, or data mappers—they remain centralized, coherent, and maintainable as the system evolves.
TL;DR: While this documentation site aims to be helpful, the source code and tests are the ultimate reference.
Following the philosophy that inspired this project, the best documentation of a system is its source code —its structure, its behavior, and its tests.
Tests should act as executable specifications: they describe what a model does, how it reacts to invalid states, and how it protects its own consistency. They are also the first user of the system, providing early feedback on how natural or awkward the design feels.
For this reason, self-assert's test suite
isn’t just about correctness—it’s also meant to serve as a practical
guide to how the library works and how to use it.
npm install self-assert