assertion library


BDD assertion library.

Lead Maintainer - Colin Ihrig


const Code = require('code');
const expect = Code.expect;

expect('this string').to.only.include(['this', 'string']);


code was created as a direct rewrite of the powerful chai assertions library. This virtual fork was created for a few reasons. First, chai mixed usage of methods and properties creates a problematic environment in which it is too easy to forget a method () and result in an assertion that is never executed (and therefor passes incorrectly). This observation was noted by the must author.

The second reason is that similar to lab, our test runner, we wanted an assertion library that is small, simple, and intuitive - without plugins, extensions, or the overhead of having to support testing in the browser. code provides much of the same functionality in about 300 lines of code that are trivial to read in a few minutes.

And last, we wanted to experiment with some new features that allow deeper integration between the test runner and assertions library. The first of which are two methods exported (and used by lab) for getting the total assertions count (which is a measure of the tests comprehensiveness), and by verifying that every assertion created (e.g. every expect() call) is also executed. This will alert when a statement like expect(5) is not allowed to remain unnoticed (and fail to throw due to the missing ()).

Like lab, the goal is to keep this module small and simple. If you need extensibility or other functionality, we recommend looking at the many other excellent assertions libraries available.


See the API Reference.