Expect

Minimalistic BDD assertion toolkit based on should.js

expect(window.r).to.be(undefined);
expect({ a: 'b' }).to.eql({ a: 'b' })
expect(5).to.be.a('number');
expect([]).to.be.an('array');
expect(window).not.to.be.an(Image);

The future of Expect(.js)

Reference Automattic#100 It seems that https://github.com/LearnBoost is too busy with his work, and our beloved assertion library has not been updated for months, so I decided to fork it to my own Github account and started reviewing all PR, one by one.

Breaking changes:

• be is no longer a method, i.e you can not use be()
• eql' is now an alias equal`, which you usually want to use for equality assertion, except in the next 2 following cases
• resemble is use to assert if 2 object looks like each other, i.e. == comparison
• identical is use to assert if 2 variables refer to the same object, i.e.

expect([]).not.to.be.identical([]);
var arr = [];
expect(arr).not.to.be.identical(arr);

• We shall contact https://www.npmjs.org/~onirame to claim npm package name expect, as this package was last updated 2 years ago, ref. So you might in the future use npm install expect and var expect = require('expect'). In the mean time, in your package.json, you can use "mocha": "git://github.com/truongsinh/expect"

Contribution

Ideas and PRs are welcome

1. If you are fixing a bug, do it in BDD manner, i.e. write a test case that fails first, then modify the library such that it passes that test case.

2. If you are developing a new feature, ask yourself should it be in core or a plugin. Issues page is the best place to discuss. We shall keep a list of available plugin in this README (or a separate list in a far future when it is too crowded). Take a look at expect.core to see how "core" plugin is implemented.

3. Fell free to bump package.json, bower.json and expect.version build number, for example "0.2.1-dev", and remember to keep it consistent between the 3.

4. All PR are subject to be modified, such as code format, version number.

Features

• Cross-browser: works on IE6+, Firefox, Safari, Chrome, Opera.
• Compatible with all test frameworks.
• Node.JS ready (require('expect.js')).
• Standalone. Single global with no prototype extensions or shims.

How to use

Node

Install it with NPM or add it to your package.json:

$ npm install expect.js

Then:

var expect = require('expect.js');

Browser

Expose the expect.js found at the top level of this repository.

<script src="expect.js"></script>

API

There are 4 terminal flag: ok, throw, empty, fail. The rest are chainable, i.e. you can use and after them.

and: make chainable asserts

expect([1, 2]).not.be.empty().and.to.contain(1).and.to.contain(2).and.not.to.contain(3);

ok: asserts that the value is truthy or not.

expect(1).to.be.ok();
expect(true).to.be.ok();
expect({}).to.be.ok();
expect(0).to.not.be.ok();

equal / eql: asserts that two objects are equivalent

expect(1).to.equal(1);
expect(1.4 - 0.1).to.not.equal(1.3); // see approximate
expect(NaN).not.to.equal(NaN);
expect(1).not.to.equal(true);
expect('1').to.not.equal(1);
expect({a: 3}).to.equal({a: 3}); // see identical
expect({a: 3}).not.to.equal({a: 4});
expect({a: 3}).not.to.equal({b: 3});

approximately / approximate: handy for float rounding error.

expect(1.4 - 0.1).to.be.approximately(1.3, 1e-15);
expect(99.99).approximate(100, 0.1);

resemble: asserts loose equality ==

expect(1).to.resemble('1');
expect(0).to.resemble(false);

a/an: asserts typeof with support for array type and instanceof.

// typeof with optional `array`
expect(5).to.be.a('number');
expect([]).to.be.an('array');  // works
expect([]).to.be.an('object'); // works too, since it uses `typeof`

// constructors
expect(5).to.be.a(Number);
expect([]).to.be.an(Array);
expect(tobi).to.be.a(Ferret);
expect(person).to.be.a(Mammal);

match: asserts String regular expression match.

expect(program.version).to.match(/[0-9]+\.[0-9]+\.[0-9]+/);

contain: asserts indexOf for an array or string, or child key-value for an object.

expect([1, 2]).to.contain(1);
expect('hello world').to.contain('world');
expect({ foo: 'bar', bar: 'foo' }).to.contain({ bar: 'foo' });
expect({ foo: 'bar' }).to.not.contain({ foo: 'baz' });

length: asserts array .length.

expect([]).to.have.length(0);
expect([1,2,3]).to.have.length(3);

empty: asserts that an array is empty or not.

expect([]).to.be.empty();
expect({}).to.be.empty();
expect({ length: 0, duck: 'typing' }).to.be.empty();
expect({ my: 'object' }).to.not.be.empty();
expect([1,2,3]).to.not.be.empty();

property: asserts presence of an own property (and value optionally).

expect(window).to.have.property('expect')
expect(window).to.have.property('expect', expect)
expect({a: 'b'}).to.have.property('a');

key/keys: asserts the presence of a key. Supports the only modifier.

expect({ a: 'b' }).to.have.key('a');
expect({ a: 'b', c: 'd' }).to.only.have.keys('a', 'c');
expect({ a: 'b', c: 'd' }).to.only.have.keys(['a', 'c']);
expect({ a: 'b', c: 'd' }).to.not.only.have.key('a');

throwException/throwError: asserts that the Function throws or not when called.

expect(fn).to.throwError(); // synonym of throwException
expect(fn).to.throwException(function (e) { // get the exception object
  expect(e).to.be.a(SyntaxError);
});
expect(fn).to.throwException(/matches the exception message/);
expect(fn2).to.not.throwException();

withArgs: creates anonymous function to call fn with arguments.

expect(fn).withArgs(invalid, arg).to.throwException();
expect(fn).withArgs(valid, arg).to.not.throwException();

within/between: asserts a number within a range.

expect(1).to.be.within(0, Infinity)
expect(2).to.be.between(1, 3);

greaterThan/above: asserts >.

expect(3).to.be.above(0);
expect(5).to.be.greaterThan(3);

lessThan/below: asserts <.

expect(0).to.be.below(3);
expect(1).to.be.lessThan(3);

fail: explicitly forces failure.

expect().fail()
expect().fail("Custom failure message")

Using with a test framework

For example, if you create a test suite with mocha.

Let's say we wanted to test the following program:

math.js

function add (a, b) { return a + b; };

Our test file would look like this:

describe('test suite', function () {
  it('should expose a function', function () {
    expect(add).to.be.a('function');
  });

  it('should do math', function () {
    expect(add(1, 3)).to.equal(4);
  });
});

If a certain expectation fails, an exception will be raised which gets captured and shown/processed by the test runner.

Differences with should.js

• No need for static should methods like should.strictEqual. For example, expect(obj).to.be(undefined) works well.
• Some API simplifications / changes.
• API changes related to browser compatibility.

Running tests

Clone the repository and install the developer dependencies:

git clone git://github.com/LearnBoost/expect.js.git expect
cd expect && npm install

Node

make test

Browser

make test-browser

and point your browser(s) to http://localhost:3000/test/

Credits

(The MIT License)

Copyright (c) 2014 TruongSinh Tran-Nguyen <[email protected]> (c) 2011 Guillermo Rauch <[email protected]>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

3rd-party

Heavily borrows from should.js by TJ Holowaychuck - MIT.