Agree is a library for implementing Contract Programming /
Design by contract in JavaScript,
including preconditions, postconditions and class invariants.
It is inspired by projects like contracts.coffee, but requires no build steps, no non-standard language features, and is introspectable.
Experimental as of November 2016.
- Functions, method and class invariants work
- Support for asyncronous functions using Promise (ES6/A+ compatible)
- Contracts can be reusable, and used to define interfaces (having multiple implementations)
- Some proof-of-concept documentation and testing tools exists
- Library has not been used in any real applications yet
- Lock down the core contracts API
- Add more tests for core functionality
- Do use-case exploration of a browser/frontend example
- Run all automated tests under browser
- Stabilize and document the testing and documentation tools
Future
- Support postcondition expressions that contain function inputs
- Support postconditions expressions matching against 'old' instance members
- Support invariants on properties
For details see TODO/FIXME/XXX/MAYBE comments in the code.
Add Agree to your project using NPM
npm install --save agree
npm install --save-dev agree-tools
MIT, see LICENSE.md
See the tests under ./spec/ for full reference.
agree-tools uses the introspection features of Agree to provide support for testing and documentation, driven by the contracts/code.
- No special dependencies, works anywhere (browser, node.js, etc), usable as library
- That contracts are used is completely transparent to consuming code
- Can start using contracts stepwise, starting with just some functions/methods
- JavaScript-friendly fluent API (even if written with CoffeeScript)
- Preconditions can, and are encouraged to, be used for input validation
Usecases
- HTTP REST apis: specifying behavior, validating request, consistent error handling
- NoFlo components: verifying data on inports, specifying component behavior
- Interfaces: multiple implementations of same interface fully described
Functions, classes and instances built with Agree know their associated contracts. This allows to query the code about its properties, to generate documentation, test-cases and aid in debugging of failures.
Agree is partially related other work by author on introspectable programming, including Finito (finite state machines) and NoFlo/MicroFlo (dataflow).