airbnbjest-wrap 
Fluent pluggable interface for easily wrapping describe, it, and test blocks in Jest tests.
Example
var wrap = require('jest-wrap');
var expect = require('chai').expect;
var mockWindow = {
location: {
href: 'test/url'
}
};
wrap().withGlobal('window', () => mockWindow).describe('mocked window', function () {
it('is mocked', function () {
expect(window).to.equal(mockWindow);
});
it('has the right URL', function () {
expect(window.location.href).to.equal('test/url');
});
});
var obj = { a: 1 };
wrap().withOverrides(() => obj, () => ({ a: 2, b: 3 })).describe('overridden object keys', function () {
it('has "b"', function () {
expect(obj.b).to.equal(3);
});
it('has overridden "a"', function () {
expect(obj.a).to.equal(2);
});
});
wrap().withOverride(() => obj, 'a', () => 4).skip().describe('this test is skipped', function () {
it('also supports .only()!', function () {
expect(true).to.equal(false); // skipped
});
});Plugins
A jest-wrap plugin is a named function that returns a JestWrapper instance or a descriptor object.
- A plugin’s function
namemust begin with the string “with”. - Plugins can be globally registered, or
.used ad-hoc..userequires a plugin function as its first argument; further arguments are passed through to the plugin..extendrequires a non-empty description string, and a descriptor object which may contain a value that is a function, or an array of functions, whose keys correspond to any or all of the supported jest methods.
Globally registered plugins,
.usecalls, and.extendcalls can be chained, stored, and reused - each link in the chain creates a new instance of a JestWrapper.A descriptor object may contain any or all of these 5 keys:
- a
descriptionstring, for use in “describe” and/or “it” (this is required when returning an object) beforeEach: a function, or array of functions, for use in ajestbeforeEachfunctionafterEach: a function, or array of functions, for use in ajestafterEachfunctionbeforeAll: a function, or array of functions, for use in ajestbeforeAllfunctionafterAll: a function, or array of functions, for use in ajestafterAllfunction
- a
The most common approach will be for a plugin function to return this.extend(description, descriptor).
A plugin function must have a name that starts with “with”, and will be invoked with a receiver (”this” value) of a JestWrapper instance.
To register a plugin, call the register function on jest-wrap with the plugin function. This should not be done in a reusable module.
module.exports = function withFoo(any, args, you, want) {
return this.extend('with some foo stuff', {
beforeEach: function () {
// setup ran before each test
},
afterEach: [
function () {
// teardown ran after each test
},
function () {
// more teardown
}
],
beforeAll: function () {
// setup ran once before all tests
},
afterAll: function () {
// teardown ran once after all tests
}
});
};Usage
var wrap = require('jest-wrap');
wrap.register(require('jest-wrap-with-foo'));
wrap().withFoo().describe…skip/only
Although jest has describe.skip, describe.only, it.skip, it.only, test.skip, and test.only, it is not possible to implement these in jest-wrap without using ES5 property accessors. Since this project supports ES3, we decided to use .skip().describe etc rather than forfeit the ability to have skip/only.
Tests
Simply clone the repo, npm install, and run npm test