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, 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.

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.

Breaking changes for 4.x

Please check wiki.

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);

// If the object was created with Object.create(null)
// then it doesn't inherit `Object.prototype`, so it will not have `.should` getter
// so you can do:
should(user).have.property('name', 'tj');

// also you can test in that way for null's
should(null).not.be.ok;

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

To begin

1. Install it:

   $ npm install should --save-dev
   

2. Require it and use:

   var should = require('should');
   
   (5).should.be.exactly(5).and.be.a.Number;
   

In browser

Well, even when browsers by complains of authors has 100% es5 support, it does not mean it has not bugs. Please see wiki for known bugs.

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:

$ npm install
$ gulp script

The script is exported to window.Should. It is the same as using should statically:

Should(5).be.exactly(5)

Also, in the case of node.js, Object.prototype is extended with should (hence the capital S in window.Should):

window.should.be.exactly(window);
// the same
// window is host object
should.be.exactly(window);
// you should not really care about it

(5).should.be.exactly(5);

You can easy install it with npm or bower:

npm install should --save-dev
# or
bower install shouldjs/should.js

Static should and assert module

For some rare cases should can be used statically, without Object.prototype. It can be a replacement for the node assert module:

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)

.not

.not negates the current assertion.

.any

.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.

Assertions

chaining assertions

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

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

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.

.ok

Assert that a chained object is truthy in javascript (ie: not '', null, undefined, 0 , NaN).

Assert truthfulness:

true.should.be.ok;
'yay'.should.be.ok;
(1).should.be.ok;
({}).should.be.ok;

or negated:

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

Warning: No assertions can be performed on null and undefined values. e.g.

  undefined.should.not.be.ok;

will give you Uncaught TypeError: Cannot read property 'should' of undefined).

In order to test for null use

(err === null).should.be.true;

.true

Assert if a chained object === true:

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

.false

Assert if a chained object === false:

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

.eql(otherValue)

Asserts if a chained object is equal to otherValue. The object is compared by its actual content, not just reference equality.

({ foo: 'bar' }).should.eql({ foo: 'bar' });
[1,2,3].should.eql([1,2,3]);
// see next example it is correct, even if it is different types, but actual content the same
[1, 2, 3].should.eql({ '0': 1, '1': 2, '2': 3 });

.equal(otherValue) and .exactly(otherValue)

Asserts if a chained object is strictly equal to otherValue (using ===). It means primitive values compared as is (there is no any type conversion) and reference values compared by references.

(4).should.equal(4);
'test'.should.equal('test');
[1,2,3].should.not.equal([1,2,3]);
(4).should.be.exactly(4);

.startWith(str)

Assert that a string starts with str.

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

.endWith(str)

Assert that a string ends with str.

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

.within(from, to)

Assert inclusive numeric range (<= to and >= from):

user.age.should.be.within(5, 50);
(5).should.be.within(5, 10).and.within(5, 5);

.approximately(num, delta)

Assert a floating point number is near num within the delta margin:

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

.above(num) and .greaterThan(num)

Assert a numeric value is above the given value (> num):

user.age.should.be.above(5);
user.age.should.not.be.above(100);
(5).should.be.above(0);
(5).should.not.be.above(5);

.below(num) and .lessThan(num)

Assert a numeric value is below the given value (< num):

user.age.should.be.below(100);
user.age.should.not.be.below(5);
(5).should.be.below(6);
(5).should.not.be.below(5);

.NaN

Assert a numeric value is NaN:

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

.Infinity

Assert a numeric value is Infinity:

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

.type(str)

Assert a given object is of a particular type (using typeof operator):

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

.instanceof(constructor) and .instanceOf(constructor)

Assert a given object is an instance of constructor (using instanceof operator):

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

.arguments

Assert a given object is an Arguments:

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

.Object, .Number, .Array, .Boolean, .Function, .String, .Error

Assert a given object is instance of the given constructor (shortcut for .instanceof assertion).

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

.enumerable(name[, value])

Assert a property exists, is enumerable, and has an optional value (compare using .eql):

'asd'.should.not.have.enumerable('0');
user.should.have.enumerable('name');
user.should.have.enumerable('age', 15);
user.should.not.have.enumerable('rawr');
user.should.not.have.enumerable('age', 0);
[1, 2].should.have.enumerable('0', 1);

.property(name[, value])

Assert property exists and has an optional value (compare using .eql):

user.should.have.property('name');
user.should.have.property('age', 15);
user.should.not.have.property('rawr');
user.should.not.have.property('age', 0);
[1, 2].should.have.property('0', 1);

NB .property changes the chain's object to the given property's value, so be careful when chaining after .property!

.properties(propName1, propName2, ...) or .properties([propName1, propName2, ...]) or .properties(obj)

obj should be an object that maps properties to their actual values.

Assert all given properties exist and have given values (compare using .eql):

user.should.have.properties('name', 'age');
user.should.have.properties(['name', 'age']);
user.should.have.properties({
    name: 'denis',
    age: 24
});

.length(number) and .lengthOf(number)

Assert length property exists and has a value of the given number (shortcut for .property('length', number)):

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

NB .length and .lengthOf change the chain's object to the given length value, so be careful when chaining!

.ownProperty(str) and .hasOwnProperty(str)

Assert given object has own property (using .hasOwnProperty):

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

NB .ownProperty and .hasOwnProperty change the chain's object to the given property value, so be careful when chaining!

.empty

Assert given value is empty. Strings, arrays, arguments with a length of 0, and objects without their own properties, are considered empty.

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

.keys([key1, key2, ...]) and .keys(key1, key2, ...) and .key(key)

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']);
({}).should.have.keys();
({}).should.have.keys('key'); //fail AssertionError: expected {} to have key 'key'missing keys: 'key'

.propertyByPath([name1, ...]) or .propertyByPath(name1, name2, ...)

Assert property exists and has optional value (compare using .eql):

var obj = { foo: 'bar', baz: 'raz', zad: { a: 10 } };
obj.should.have.propertyByPath('zad', 'a');
obj.should.not.have.propertyByPath(0, 1, 2);

NB .propertyByPath changes the chain's object to the given property's value if found

.containEql(otherValue)

Assert given value to contain something .eql to otherValue. See examples to understand better:

'hello boy'.should.containEql('boy');
[1,2,3].should.containEql(3);
[[1],[2],[3]].should.containEql([3]);
[[1],[2],[3, 4]].should.not.containEql([3]);

({ b: 10 }).should.containEql({ b: 10 });
([1, 2, { a: 10 }]).should.containEql({ a: 10 });
[1, 2, 3].should.not.containEql({ a: 1 });

[{a: 'a'}, {b: 'b', c: 'c'}].should.containEql({a: 'a'});
[{a: 'a'}, {b: 'b', c: 'c'}].should.not.containEql({b: 'b'});

When .containEql check arrays it check elements to be in the same order in otherValue and object just to be presented.

.containDeep(otherValue)

Assert given value to contain something .eql to otherValue within depth. Again see examples:

'hello boy'.should.containDeep('boy');
[1,2,3].should.containDeep([3]);
[1,2,3].should.containDeep([1, 3]);
//but not
[1,2,3].should.containDeep([3, 1]);

({ a: { b: 10 }, b: { c: 10, d: 11, a: { b: 10, c: 11} }}).should
  .containDeep({ a: { b: 10 }, b: { c: 10, a: { c: 11 }}});

[1, 2, 3, { a: { b: { d: 12 }}}].should.containDeep([{ a: { b: {d: 12}}}]);

[[1],[2],[3]].should.containDeep([[3]]);
[[1],[2],[3, 4]].should.containDeep([[3]]);
[{a: 'a'}, {b: 'b', c: 'c'}].should.containDeep([{a: 'a'}]);
[{a: 'a'}, {b: 'b', c: 'c'}].should.containDeep([{b: 'b'}]);

It does not search somewhere in depth it check all pattern in depth. Objects are checked by properties key and value; arrays are checked like sub sequences. Everyting is compared using .eql. Main difference with .containEql is that this assertion requires full type chain - if asserted value is an object, otherValue should be also an object (which is sub object of given). The same is true for arrays, otherValue should be an array which compared to be subsequence of given object.

Also exists assertion .containDeepOrdered which check arrays in the same order.

.match(otherValue)

Assert given object matches otherValue.

Given: String, otherValue: regexp. Uses RegExp#exec(str):

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

Given: Array, otherValue: regexp - assert each value match to regexp.

['a', 'b', 'c'].should.match(/[a-z]/);
['a', 'b', 'c'].should.not.match(/[d-z]/);

Given: Object, otherValue: regexp - assert own property's values to match regexp.

({ a: 'foo', c: 'barfoo' }).should.match(/foo$/);
({ a: 'a' }).should.not.match(/^http/);

Given: Anything, otherValue: function - assert if given value matched to function.

Function can use .should inside or return 'true' or 'false', in all other cases it do nothing. If you return value that return assertion, you will receive better error messages.

(5).should.match(function(n) { return n > 0; });
(5).should.not.match(function(n) { return n < 0; });
(5).should.not.match(function(it) { it.should.be.an.Array; });
(5).should.match(function(it) { return it.should.be.a.Number; });

Now compare messages:

(5).should.not.match(function(it) { it.should.be.a.Number; });
//AssertionError: expected 5 not to match [Function]
(5).should.not.match(function(it) { return it.should.be.a.Number; });
//AssertionError: expected 5 not to match [Function]
//	expected 5 to be a number

Given: object, otherValue: another object - assert that object properties match to properties of another object in meaning that describe above cases. See examples:

({ a: 10, b: 'abc', c: { d: 10 }, d: 0 }).should
    .match({ a: 10, b: /c$/, c: function(it) { return it.should.have.property('d', 10); }});

[10, 'abc', { d: 10 }, 0].should
	.match({ '0': 10, '1': /c$/, '2': function(it) { return it.should.have.property('d', 10); } });

[10, 'abc', { d: 10 }, 0].should
    .match([10, /c$/, function(it) { return it.should.have.property('d', 10); }]);

.matchEach(otherValue)

Assert given property keys and values each match given check object.

If otherValue is RegExp, then each property value checked to match it:

(['a', 'b', 'c']).should.matchEach(/[a-c]/);

If otherValue is Function, then check each property value and key matched it:

[10, 11, 12].should.matchEach(function(it) { return it >= 10; });
[10, 11, 12].should.matchEach(function(it) { return it >= 10; });

In other cases it checks that each property value is .eql to otherValue:

[10, 10].should.matchEach(10);

.throw() and throwError()

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 error message matches regexp:

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

Error properties to match some other properties (used .match):

var error = new Error();
error.a = 10;
(function(){ throw error; }).should.throw({ a: 10 });

(function(){ throw error; }).should.throw(Error, { a: 10 });

If you need to pass arguments and/or context to execute function use Function#bind(context, arg1, ...):

function isPositive(n) {
    if(n <= 0) throw new Error('Given number is not positive')
}

isPositive.bind(null, 10).should.not.throw();
isPositive.bind(null, -10).should.throw();

If you need to check something in an asynchronous function, you must do it in 2 steps:

// first we need to check that function is called
var called = false;
collection.findOne({ _id: 10 }, function(err, res) {
    called = true;

    //second we test what you want
    res.should.be....
});

called.should.be.true;

In case you are using something like Mocha, you should use an asynchronous test, and call done() in the proper place to make sure that your asynchronous function is called before the test finishes.

collection.findOne({ _id: 10 }, function(err, res) {
    if(err) return done(err);
    //second we test what you want
    res.should.be....

    done();
});

In general, if you need to check that something is executed, you are best using spies. A good example is sinon.

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: 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, instanceof, above, below, match, length, ownProperty.

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+$/);
  });
});

Adding own assertions

To add own assertion you need to call should.Assertion.add function. It accept 3 arguments:

1. name of assertion method (string)
2. assertion function (function)
3. optional boolean value to mark if this assertion should be getter

What assertion function should do. It should check only positive case. should will handle .not itself. this in assertion function will be instance of should.Assertion and you must define in any way this.params object in your assertion function call before assertion check happen.

params object can contain several fields:

• operator - it is string which describe your assertion
• obj it is actual value, you can assume it is your own this.obj if you need to define you own
• expected it is any value that expected to be matched this.obj

You can assume its usage in generating AssertionError message like: expected obj? || this.obj not? operator expected?

In should sources appeared 2 kinds of usage of this method.

First not preferred and used only for shortcuts to other assertions, e.g how .should.be.true defined:

Assertion.add('true', function() {
    this.is.exactly(true);
}, true);

There you can see that assertion function do not define own this.params and instead call within the same assertion .exactly that will fill this.params. You should use this way very carefully, but you can use it.

Second way preferred and i assume you will use it instead of first.

Assertion.add('true', function() {
    this.params = { operator: 'to be true', expected: true };

    this.obj.should.be.exactly(true);
}, true);

in this case this.params defined and then used new assertion context (because called .should). Internally this way does not create any edge cases as first.

Assertion.add('asset', function() {
    this.params = { operator: 'to be asset' };

    this.obj.should.have.property('id').which.is.a.Number;
    this.obj.should.have.property('path');
})

//then
> ({ id: '10' }).should.be.an.asset();
AssertionError: expected { id: '10' } to be asset
    expected '10' to be a number

> ({ id: 10 }).should.be.an.asset();
AssertionError: expected { id: 10 } to be asset
    expected { id: 10 } to have property path

Contributions

Actual list of contributors if you want to show it your friends.

To run the tests for should simply run:

$ make test

See also CONTRIBUTING.

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

MIT © 2010-2014 TJ Holowaychuk