should

What is should?

The 'should' npm package is an expressive, readable, framework-agnostic assertion library for Node.js and browsers. It extends the 'Object.prototype' with a single non-enumerable getter that allows you to express how your code should behave in a readable way. It can be used for writing tests and supports both BDD (Behavior-Driven Development) and TDD (Test-Driven Development) styles.

What are should's main functionalities?

Chainable Assertions

Allows chaining multiple assertions together for readability and expressiveness.

should(value).be.exactly(42).and.be.a.Number();

Type Assertions

Provides assertions to check the type of a variable.

should('test').be.a.String();

Number Assertions

Includes assertions specifically for numbers, such as checking if a number is within a range.

should(10).be.above(5).and.below(15);

Property Assertions

Allows asserting the presence and value of an object's property.

should({ name: 'Alice', age: 25 }).have.property('name', 'Alice');

Equality Assertions

Enables asserting deep equality between objects or arrays.

should([1, 2, 3]).eql([1, 2, 3]);

Error Assertions

Provides a way to assert that a function throws an error.

should(function() { throw new Error('fail'); }).throw();

Other packages similar to should

chai

Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework. It offers similar functionality to 'should' with chainable assertions but has a different syntax and additional interfaces like 'expect' and 'assert'.

expect.js

Expect.js is a minimalistic BDD-style assertions library that can be used in Node.js or in the browser. It provides a similar API to 'should' but does not extend 'Object.prototype', which can be a desirable feature for some users to avoid potential conflicts.

assert

Assert is a module that provides a simple set of assertion tests that can be used to test invariants. It is built into Node.js and offers a more traditional TDD assertion style, which is different from the BDD style provided by 'should'.

jest

Jest is a delightful JavaScript Testing Framework with a focus on simplicity. It comes with its own assertion library and test runner. While it provides similar assertion capabilities, it is more than just an assertion library as it includes testing utilities and is often used as a complete testing solution.

README

should.js

should is an expressive, readable, test framework agnostic, assertion library for node.

It extends the Object prototype with a single non-enumerable getter that allows you to express how that object should behave.

Example

var should = require('should');

var user = {
    name: 'tj'
  , pets: ['tobi', 'loki', 'jane', 'bandit']
};

user.should.have.property('name', 'tj');
user.should.have.property('pets').with.lengthOf(4);

// or without Object.prototype, for guys how did Object.create(null)
should(user).have.property('name', 'tj');
should(true).ok;

someAsyncTask(foo, function(err, result){
  should.not.exist(err);
  should.exist(result);
  result.bar.should.equal(foo);
});

Installation

$ npm install should --save-dev

In browser

If you want to use should in browser, use version that is in root of repository. It is build with browserify (see Makefile about how it is build). To build fresh version:

# you should have browserify
npm install -g browserify
make browser

chaining assertions

Every assertion will return a should.js-wraped Object, so assertions can be chained. For example:

user.should.be.an.instanceOf(Object).and.have.property('name', 'tj');
user.pets.should.be.instanceof(Array).and.have.lengthOf(4);

All assertions return themselves but not property and ownProperty. They two would return the property value.

for example if a property is volatile we can first assert property existence:

// `user.should.have.property('pets')` returned `should(user.pets)` but not `should(user)`
user.should.have.property('pets').with.lengthOf(4)

which is essentially equivalent to below, however the property may not exist:

user.pets.should.have.lengthOf(4)

our dummy getters such as a, an, be, of and have make tests more readable while the getters and and with helps express chaining:

user.should.be.an.instanceOf(Object).and.have.property('name', 'tj')
user.should.have.property('pets').with.a.lengthOf(4)

Those getters don't have any actual effect, just for readability.

static

For some rare cases should can be used statically, without Object.prototype. It can be replacement for node assert module (and it uses the same AssertionError):

assert.fail(actual, expected, message, operator) // just write wrong should assertion
assert(value, message), assert.ok(value, [message]) // should(value).ok
assert.equal(actual, expected, [message]) // should(actual).eql(expected, [message])
assert.notEqual(actual, expected, [message]) // should(actual).not.eql(expected, [message])
assert.deepEqual(actual, expected, [message]) // should(actual).eql(expected, [message])
assert.notDeepEqual(actual, expected, [message]) // should(actual).not.eql(expected, [message])
assert.strictEqual(actual, expected, [message]) // should(actual).equal(expected, [message])
assert.notStrictEqual(actual, expected, [message]) // should(actual).not.equal(expected, [message])
assert.throws(block, [error], [message]) // should(block).throw([error])
assert.doesNotThrow(block, [message]) // should(block).not.throw([error])
assert.ifError(value) // should(value).Error (to check if it is error) or should(value).not.ok (to check that it is falsy)

ok

Assert truthfulness:

true.should.be.ok
'yay'.should.be.ok
(1).should.be.ok

or negated:

false.should.not.be.ok
''.should.not.be.ok
(0).should.not.be.ok

true

Assert === true:

true.should.be.true
'1'.should.not.be.true

false

Assert === false:

false.should.be.false
(0).should.not.be.false

arguments

Assert Arguments:

var args = (function(){ return arguments; })(1,2,3);
args.should.be.arguments;
[].should.not.be.arguments;

empty

Asserts that given object is empty

[].should.be.empty
''.should.be.empty
({}).should.be.empty
(function() {
  arguments.should.be.empty;
})()

eql

equality:

({ foo: 'bar' }).should.eql({ foo: 'bar' })
[1,2,3].should.eql([1,2,3])

equal and exactly

strict equality:

should.strictEqual(undefined, value)
should.strictEqual(false, value)
(4).should.equal(4)
'test'.should.equal('test')
[1,2,3].should.not.equal([1,2,3])
(4).should.be.exactly(4)

within

Assert inclusive numeric range:

user.age.should.be.within(5, 50)

approximately

Assert floating point number:

(99.99).should.be.approximately(100, 0.1);

type

Assert typeof:

user.should.be.type('object')
'test'.should.be.type('string')

instanceof and instanceOf

Assert instanceof or instanceOf:

user.should.be.an.instanceof(User)
[].should.be.an.instanceOf(Array)

above

Assert numeric value above the given value:

user.age.should.be.above(5)
user.age.should.not.be.above(100)

below

Assert numeric value below the given value:

user.age.should.be.below(100)
user.age.should.not.be.below(5)

NaN

Assert numeric valus is NaN:

(undefined + 0).should.be.NaN;

Infinity

Assert numeric valus is Infinity:

(1/0).should.be.Infinity;

match

Assert regexp match:

username.should.match(/^\w+$/)

length

Assert length property exists and has a value of the given number:

user.pets.should.have.length(5)
user.pets.should.have.a.lengthOf(5)
({ length: 10}).should.have.length(10);

Aliases: lengthOf

property

Assert property exists and has optional value:

user.should.have.property('name')
user.should.have.property('age', 15)
user.should.not.have.property('rawr')
user.should.not.have.property('age', 0)

properties

Assert given properties exists:

user.should.have.properties('name', 'age');
user.should.have.properties(['name', 'age']);

ownProperty

Assert own property (on the immediate object):

({ foo: 'bar' }).should.have.ownProperty('foo')

status(code)

Asserts that .statusCode is code:

res.should.have.status(200);

header(field[, value])

Asserts that a .headers object with field and optional value are present:

res.should.have.header('content-length');
res.should.have.header('Content-Length', '123');
res.should.have.header('content-length', '123');

json

Assert that Content-Type is "application/json; charset=utf-8"

res.should.be.json

html

Assert that Content-Type is "text/html; charset=utf-8"

res.should.be.html

include(obj) or contain(obj)

Assert that the given obj is present via indexOf(), so this works for strings, arrays, or custom objects implementing indexOf. Also it can assert if given object will have some sub-object.

Assert array value:

[1,2,3].should.include(3)
[1,2,3].should.include(2)
[1,2,3].should.not.include(4)

Assert substring:

'foo bar baz'.should.include('foo')
'foo bar baz'.should.include('bar')
'foo bar baz'.should.include('baz')
'foo bar baz'.should.not.include('FOO')

Assert object includes another object:

var tobi = { name: 'Tobi', age: 1 };
var jane = { name: 'Jane', age: 5 };
var user = { name: 'TJ', pet: tobi };

user.should.include({ pet: tobi });
user.should.include({ pet: tobi, name: 'TJ' });
user.should.not.include({ pet: jane });
user.should.not.include({ name: 'Someone' });

includeEql(obj)

Assert that an object equal to the given obj is present in an Array:

[[1],[2],[3]].should.includeEql([3])
[[1],[2],[3]].should.includeEql([2])
[[1],[2],[3]].should.not.includeEql([4])

throw()

Assert an exception is thrown:

(function(){
  throw new Error('fail');
}).should.throw();

Assert an exception is not thrown:

(function(){

}).should.not.throw();

Assert exception message matches string:

(function(){
  throw new Error('fail');
}).should.throw('fail');

Assert exepection message matches regexp:

(function(){
  throw new Error('failed to foo');
}).should.throw(/^fail/);

throwError()

An alias of throw, its purpose is to be an option for those who run jshint in strict mode.

(function(){
  throw new Error('failed to baz');
}).should.throwError(/^fail.*/);

startWith(str)

Assert that string starts with str.

'foobar'.should.startWith('foo')
'foobar'.should.not.startWith('bar')

endWith(str)

Assert that string ends with str.

'foobar'.should.endWith('bar')
'foobar'.should.not.endWith('foo')

keys

Assert own object keys, which must match exactly, and will fail if you omit a key or two:

var obj = { foo: 'bar', baz: 'raz' };
obj.should.have.keys('foo', 'baz');
obj.should.have.keys(['foo', 'baz']);

type assertions

({}).should.be.an.Object;
(1).should.be.an.Number;
[].should.be.an.Array;
(true).should.be.a.Boolean;
''.should.be.a.String;

Optional Error description

As it can often be difficult to ascertain exactly where failed assertions are coming from in your tests, an optional description parameter can be passed to several should matchers. The description will follow the failed assertion in the error:

(1).should.eql(0, 'some useful description')

AssertionError: expected 1 to equal 0 | some useful description
  at Object.eql (/Users/swift/code/should.js/node_modules/should/lib/should.js:280:10)
  ...

The methods that support this optional description are: eql, equal, within, a, instanceof, above, below, match, length, property, ownProperty, include, and includeEql.

Mocha example

For example you can use should with the Mocha test framework by simply including it:

var should = require('should');
var mylib = require('mylib');


describe('mylib', function () {
  it('should have a version with the format #.#.#', function() {
    lib.version.should.match(/^\d+\.\d+\.\d+$/);
  }
});

Running tests

To run the tests for should simply run:

$ make test

OMG IT EXTENDS OBJECT???!?!@

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.

License

(The MIT License)

Copyright (c) 2010-2011 TJ Holowaychuk <[e-mail]>

Copyright (c) 2011 Aseem Kishore <[e-mail]>

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.

Changelog

2.1.0 / 2013-11-11

• Override .inspect for Date's to convert them to ISOString