# should.js
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[](https://gitter.im/shouldjs/should.js)
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[](https://travis-ci.org/shouldjs/should.js)
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[](https://saucelabs.com/u/shouldjs)
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_should_ is an expressive, readable, framework-agnostic assertion library. The main goals of this library are __to be expressive__ and __to be helpful__. It keeps your test code clean, and your error messages helpful.
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By default (when you `require('should')`) _should_ extends the `Object.prototype` with a single non-enumerable getter that allows you to express how that object should behave. It also returns itself when required with `require`.
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It is also possible to use should.js without getter (it will not even try to extend Object.prototype), just `require('should/as-function')`. Or if you already use version that auto add getter, you can call `.noConflict` function.
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**Results of `(something).should` getter and `should(something)` in most situations are the same**
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### Upgrading instructions
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Please check [wiki page](https://github.com/shouldjs/should.js/wiki/Breaking-changes) for upgrading instructions.
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### FAQ
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You can take look in [FAQ](https://github.com/shouldjs/should.js/wiki/FAQ).
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## Example
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```javascript
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var should = require('should');
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var user = {
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name: 'tj'
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, pets: ['tobi', 'loki', 'jane', 'bandit']
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};
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user.should.have.property('name', 'tj');
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user.should.have.property('pets').with.lengthOf(4);
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// If the object was created with Object.create(null)
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// then it doesn't inherit `Object.prototype`, so it will not have `.should` getter
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// so you can do:
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should(user).have.property('name', 'tj');
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// also you can test in that way for null's
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should(null).not.be.ok();
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someAsyncTask(foo, function(err, result){
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should.not.exist(err);
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should.exist(result);
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result.bar.should.equal(foo);
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});
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```
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## To begin
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1. Install it:
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```bash
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$ npm install should --save-dev
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```
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2. Require it and use:
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```js
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var should = require('should');
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(5).should.be.exactly(5).and.be.a.Number();
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```
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```js
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var should = require('should/as-function');
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should(10).be.exactly(5).and.be.a.Number();
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```
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3. For TypeScript users:
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```js
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import * as should from 'should';
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(0).should.be.Number();
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```
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## In browser
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Well, even when browsers by complaints of authors have 100% es5 support, it does not mean it has no bugs. Please see [wiki](https://github.com/shouldjs/should.js/wiki/Known-Bugs) for known bugs.
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If you want to use _should_ in browser, use the `should.js` file in the root of this repository, or build it yourself. To build a fresh version:
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```bash
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$ npm install
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$ npm run browser
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```
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The script is exported to `window.should`:
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```js
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should(10).be.exactly(10)
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```
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You can easy install it with npm or bower:
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```sh
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npm install should -D
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# or
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bower install shouldjs/should.js
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```
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## API docs
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Actual api docs generated by jsdoc comments and available at [http://shouldjs.github.io](http://shouldjs.github.io).
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## Usage examples
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Please look on usage in [examples](https://github.com/shouldjs/examples)
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## .not
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`.not` negates the current assertion.
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## .any
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`.any` allow for assertions with multiple parameters to assert any of the parameters (but not all). This is similar to the native JavaScript [array.some](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/some).
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# Assertions
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## chaining assertions
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Every assertion will return a `should.js`-wrapped Object, so assertions can be chained.
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To help chained assertions read more clearly, you can use the following helpers anywhere in your chain: `.an`, `.of`, `.a`, `.and`, `.be`, `.have`, `.with`, `.is`, `.which`. Use them for better readability; they do nothing at all.
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For example:
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```js
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user.should.be.an.instanceOf(Object).and.have.property('name', 'tj');
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user.pets.should.be.instanceof(Array).and.have.lengthOf(4);
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```
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Almost all assertions return the same object - so you can easy chain them. But some (eg: `.length` and `.property`) move the assertion object to a property value, so be careful.
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## Adding own assertions
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Adding own assertion is pretty easy. You need to call `should.Assertion.add` function. It accept 2 arguments:
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1. name of assertion method (string)
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2. assertion function (function)
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What assertion function should do. It should check only positive case. `should` will handle `.not` itself.
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`this` in assertion function will be instance of `should.Assertion` and you **must** define in any way this.params object
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in your assertion function call before assertion check happen.
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`params` object can contain several fields:
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- `operator` - it is string which describe your assertion
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- `actual` it is actual value, you can assume it is your own this.obj if you need to define you own
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- `expected` it is any value that expected to be matched this.obj
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You can assume its usage in generating AssertionError message like: expected `obj`? || this.obj not? `operator` `expected`?
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In `should` sources appeared 2 kinds of usage of this method.
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First not preferred and used **only** for shortcuts to other assertions, e.g how `.should.be.true()` defined:
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```javascript
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Assertion.add('true', function() {
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this.is.exactly(true);
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});
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```
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There you can see that assertion function do not define own `this.params` and instead call within the same assertion `.exactly`
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that will fill `this.params`. **You should use this way very carefully, but you can use it**.
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Second way preferred and i assume you will use it instead of first.
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```javascript
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Assertion.add('true', function() {
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this.params = { operator: 'to be true', expected: true };
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should(this.obj).be.exactly(true);
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});
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```
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in this case this.params defined and then used new assertion context (because called `.should`). Internally this way does not
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create any edge cases as first.
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```javascript
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Assertion.add('asset', function() {
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this.params = { operator: 'to be asset' };
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this.obj.should.have.property('id').which.is.a.Number();
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this.obj.should.have.property('path');
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})
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//then
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> ({ id: '10' }).should.be.an.asset();
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AssertionError: expected { id: '10' } to be asset
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expected '10' to be a number
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> ({ id: 10 }).should.be.an.asset();
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AssertionError: expected { id: 10 } to be asset
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expected { id: 10 } to have property path
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```
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## Additional projects
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* [`should-sinon`](https://github.com/shouldjs/sinon) - adds additional assertions for sinon.js
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* [`should-immutable`](https://github.com/shouldjs/should-immutable) - extends different parts of should.js to make immutable.js first-class citizen in should.js
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* [`should-http`](https://github.com/shouldjs/http) - adds small assertions for assertion on http responses for node only
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* [`should-jq`](https://github.com/shouldjs/jq) - assertions for jq (need maintainer)
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* [`karma-should`](https://github.com/seegno/karma-should) - make more or less easy to work karma with should.js
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* [`should-spies`](https://github.com/shouldjs/spies) - small and dirty simple zero dependencies spies
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## Contributions
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[Actual list of contributors](https://github.com/visionmedia/should.js/graphs/contributors) if you want to show it your friends.
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To run the tests for _should_ simply run:
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$ npm test
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See also [CONTRIBUTING](./CONTRIBUTING.md).
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## OMG IT EXTENDS OBJECT???!?!@
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Yes, yes it does, with a single getter _should_, and no it won't break your code, because it does this **properly** with a non-enumerable property.
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Also it is possible use it without extension. Just use `require('should/as-function')` everywhere.
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## License
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MIT. See LICENSE for details.
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