code

assertion library

code

BDD assertion library.

Lead Maintainer - Colin Ihrig

const Code = require('code');
const expect = Code.expect;
 
expect(true).to.be.a.boolean().and.to.not.equal(false);
expect('this string').to.only.include(['this', 'string']);

code was created as a direct rewrite of the powerful chai assertions library. This virtual fork was created for a few reasons. First, chai mixed usage of methods and properties creates a problematic environment in which it is too easy to forget a method () and result in an assertion that is never executed (and therefor passes incorrectly). This observation was noted by the must author.

The second reason is that similar to lab, our test runner, we wanted an assertion library that is small, simple, and intuitive - without plugins, extensions, or the overhead of having to support testing in the browser. code provides much of the same functionality is about 300 lines of code that are trivial to read in a few minutes.

And last, we wanted to experiment with some new features that allow deeper integration between the test runner and assertions library. The first of which are two methods exported (and used by lab) for getting the total assertions count (which is a measure of the tests comprehensiveness), and by verifying that every assertion created (e.g. every expect() call) is also executed. This will alert when a statement like expect(5).to.be.a.string is not allowed to remain unnoticed (and fail to throw due to the missing ()).

Like lab, the goal is to keep this module small and simple. If you need extensibility or other functionality, we recommend looking at the many other excellent assertions libraries available.

code supports usage of connecting words to make assertions more readable. The inclusion of these grammar elements has no impact over the assertion outcome and are used for human readability only. Every method or property of the assertion object returned by expect() returns this which allows chaining addition assertions or grammar words.

The supported words are:

  • a
  • an
  • and
  • at
  • be
  • have
  • in
  • to
const Code = require('code');
const expect = Code.expect;
 
expect(10).to.be.above(5);
expect('abc').to.be.a.string();
expect([1, 2]).to.be.an.array();
expect(20).to.be.at.least(20);
expect('abc').to.have.length(3);
expect('abc').to.be.a.string().and.contain(['a', 'b']);
expect(6).to.be.in.range(5, 6);

The following words toggle a status flag for the current assertion:

  • deep - performs a deep comparison instead of simple equality (===). Required when trying to compare objects to an identical copy that is not the same reference. Used by equal() and include().
  • not - inverses the expected result of any assertion.
  • once - requires that inclusion matches appear only once in the provided value. Used by include().
  • only - requires that only the provided elements appear in the provided value. Used by include().
  • part - allows a partial match when asserting inclusion. Used by include().
const Code = require('code');
const expect = Code.expect;
 
expect(10).to.not.be.above(20);
expect([{ a: 1 }]).to.deep.include({ a: 1 });
expect([1, 1, 2]).to.only.include([1, 2]);
expect([1, 2]).to.once.include([1, 2]);
expect([1, 2, 3]).to.part.include([1, 4]);

Note that including the same flag twice toggles the last value set. This is especially important when chaining multiple assertions in a single statement (e.g. when using the and grammar word).

Generates an assertion object where:

  • value - the reference value on which to apply the assertion rules.
  • prefix - an optional string used as an error message prefix.
const Code = require('code');
const expect = Code.expect;
 
expect(10, 'Age').to.be.above(5);

Asserts that the reference value is of a certain type.

Asserts that the reference value is an arguments object.

const Code = require('code');
const expect = Code.expect;
const func = function () { return arguments; };
expect(func()).to.be.arguments();

Asserts that the reference value is an Array.

const Code = require('code');
const expect = Code.expect;
 
expect([1, 2]).to.be.an.array();

Asserts that the reference value is a boolean.

const Code = require('code');
const expect = Code.expect;
 
expect(true).to.be.a.boolean();

Asserts that the reference value is a Buffer.

const Code = require('code');
const expect = Code.expect;
 
expect(new Buffer('')).to.be.a.buffer();

Asserts that the reference value is a Date.

const Code = require('code');
const expect = Code.expect;
 
expect(new Date()).to.be.a.date();

Asserts that the reference value is a function.

const Code = require('code');
const expect = Code.expect;
 
expect(function () {}).to.be.a.function();

Asserts that the reference value is a number.

const Code = require('code');
const expect = Code.expect;
 
expect(123).to.be.a.number();

Asserts that the reference value is an RegExp.

const Code = require('code');
const expect = Code.expect;
 
expect(/abc/).to.be.a.regexp();

Asserts that the reference value is a string.

const Code = require('code');
const expect = Code.expect;
 
expect('abc').to.be.a.string();

Asserts that the reference value is an object (excluding array, buffer, or other native objects).

const Code = require('code');
const expect = Code.expect;
 
expect({ a: '1' }).to.be.an.object();

Asserts that the reference value is equals to a predefined value.

Asserts that the reference value is true.

const Code = require('code');
const expect = Code.expect;
 
expect(true).to.be.true();

Asserts that the reference value is false.

const Code = require('code');
const expect = Code.expect;
 
expect(false).to.be.false();

Asserts that the reference value is null.

const Code = require('code');
const expect = Code.expect;
 
expect(null).to.be.null();

Asserts that the reference value is undefined.

const Code = require('code');
const expect = Code.expect;
 
expect(undefined).to.be.undefined();

Aliases: includes(), contain(), contains()

Asserts that the reference value (a string, array, or object) includes the provided values where:

  • values - a single or array of values. If the reference value is a string, the values must be strings. If the reference value is an array, the values can be any array member (deep is required to compare non-literal types). If the reference value is an object, the values can be key names, or a single object with key-value pairs to match.
const Code = require('code');
const expect = Code.expect;
 
expect('abc').to.include('ab');
expect('abc').to.only.include('abc');
expect('aaa').to.only.include('a');
expect('abc').to.once.include('b');
expect('abc').to.include(['a', 'c']);
expect('abc').to.part.include(['a', 'd']);
 
expect([1, 2, 3]).to.include(1);
expect([{ a: 1 }]).to.deep.include({ a: 1 });
expect([1, 2, 3]).to.include([1, 2]);
expect([{ a: 1 }]).to.deep.include([{ a: 1 }]);
expect([1, 1, 2]).to.only.include([1, 2]);
expect([1, 2]).to.once.include([1, 2]);
expect([1, 2, 3]).to.part.include([1, 4]);
expect([[1], [2]]).to.deep.include([[1]]);
 
expect({ a: 1, b: 2, c: 3 }).to.include('a');
expect({ a: 1, b: 2, c: 3 }).to.include(['a', 'c']);
expect({ a: 1, b: 2, c: 3 }).to.only.include(['a', 'b', 'c']);
expect({ a: 1, b: 2, c: 3 }).to.include({ a: 1 });
expect({ a: 1, b: 2, c: 3 }).to.include({ a: 1, c: 3 });
expect({ a: 1, b: 2, c: 3 }).to.part.include({ a: 1, d: 4 });
expect({ a: 1, b: 2, c: 3 }).to.only.include({ a: 1, b: 2, c: 3 });
expect({ a: [1], b: [2], c: [3] }).to.deep.include({ a: [1], c: [3] });

Aliases: startsWith(),

Asserts that the reference value (a string) starts with the provided value where:

  • value - a string.

Note that this assertion is case sensitive.

const Code = require('code');
const expect = Code.expect;
 
expect('https://example.org/secure').to.startWith('https://');

Aliases: endsWith(),

Asserts that the reference value (a string) ends with the provided value where:

  • value - a string.

Note that this assertion is case sensitive.

const Code = require('code');
const expect = Code.expect;
 
expect('http://example.org/relative').to.endWith('/relative');

Aliases: exists

Asserts that the reference value exists (not null or undefined).

const Code = require('code');
const expect = Code.expect;
 
expect(4).to.exist();
expect(null).to.not.exist();

Asserts that the reference value has a length property equal to zero or an object with no keys.

const Code = require('code');
const expect = Code.expect;
 
expect('abc').to.be.empty();

Asserts that the reference value has a length property matching the provided size or an object with the specified number of keys where:

  • size - the required size.
const Code = require('code');
const expect = Code.expect;
 
expect('abcd').to.have.length(4);

Aliases: equals()

Asserts that the reference value equals the provided value (deep is required to compare non-literal types) where:

  • value - the value to compare to.
  • options - optional object specifying comparison options. This is only used on deep comparisons, and is ignored otherwise.
const Code = require('code');
const expect = Code.expect;
 
expect(5).to.equal(5);
expect({ a: 1 }).to.deep.equal({ a: 1 });

Deep comparisons are performed using Hoek.deepEqual(). The optional options argument is passed directly to Hoek.deepEqual(). An example deep comparison which ignores object prototypes is shown below.

const Code = require('code');
const expect = Code.expect;
 
expect(Object.create(null)).to.deep.equal({}, { prototype: false });

Aliases: greaterThan()

Asserts that the reference value is greater than (>) the provided value where:

  • value - the value to compare to.
const Code = require('code');
const expect = Code.expect;
 
expect(10).to.be.above(5);

Aliases: min()

Asserts that the reference value is at least (>=) the provided value where:

  • value - the value to compare to.
const Code = require('code');
const expect = Code.expect;
 
expect(10).to.be.at.least(10);

Aliases: lessThan()

Asserts that the reference value is less than (<) the provided value where:

  • value - the value to compare to.
const Code = require('code');
const expect = Code.expect;
 
expect(10).to.be.below(20);

Aliases: max()

Asserts that the reference value is at most (<=) the provided value where:

  • value - the value to compare to.
const Code = require('code');
const expect = Code.expect;
 
expect(10).to.be.at.most(10);

Aliases: range()

Asserts that the reference value is within (from <= value <= to) the provided values where:

  • from - the start of the range (inclusive).
  • to - the end of the range (inclusive).
const Code = require('code');
const expect = Code.expect;
 
expect(10).to.be.within(10, 20);
expect(20).to.be.within(10, 20);

Asserts that the reference value is between but not equal (from < value < to) the provided values where:

  • from - the start of the range (exclusive).
  • to - the end of the range (exclusive).
const Code = require('code');
const expect = Code.expect;
 
expect(15).to.be.between(10, 20);

Asserts that the reference value is about the provided value within a delta margin of difference where:

  • value - the value to compare to.
  • delta - the allowed margin of difference.
const Code = require('code');
const expect = Code.expect;
 
expect(10).to.be.about(9, 1);

Aliases: instanceOf()

Asserts that the reference value has the provided instanceof value where:

  • type - the type value to match.
const Code = require('code');
const expect = Code.expect;
 
expect(new Date()).to.be.an.instanceof(Date);

Aliases: matches()

Asserts that the reference value is a string matching the provided regular expression where:

  • regex - the regular expression to match.
const Code = require('code');
const expect = Code.expect;
 
expect('a5').to.match(/\w\d/);

Aliases: satisfies()

Asserts that the reference value satisfies the provided validator function where:

  • validator - a function with the signature function(value) with return value true or false. The reference value is passed as the only argument to the validator function and the assertion passes if the return value is true.
const Code = require('code');
const expect = Code.expect;
 
expect('x').to.satisfy(function (value) { return value === 'x'; });

Aliases: throws

Asserts that the function reference value throws an exception when called. The provided reference function is invoked within a try-catch block and any error throws is caught and compared to the provided optional requirements where:

  • type - the instanceof value of the thrown object.
  • message a string or regular expression matching the thrown error message property. Note that a string must provide a full match.
const NodeUtil = require('util');
const Code = require('code');
const expect = Code.expect;
 
const CustomError = function (message) {
 
    Error.call(this, message);
};
 
NodeUtil.inherit(CustomError, Error)
 
const throws = function () {
 
    throw new CustomError('Oh no!');
};
 
expect(throws).to.throw(CustomError, 'Oh no!');

Make the test fail with message.

const Code = require('code');
 
Code.fail('This should not occur');

Returns the total number of assertions created using the expect() method.

const Code = require('code');
const expect = Code.expect;
 
expect(5).to.not.be.a.string();
console.log(Code.count()); // -> 1 

Returns an array of the locations where incomplete assertions were declared or null if no incomplete assertions found.

const Code = require('code');
const expect = Code.expect;
 
expect(5).to.not.be.a.string;
console.log(Code.incomplete()); // -> [ 'readme.js:667:1' ] 

code can be configured using the module's settings object. The following settings are supported:

A Boolean value that, when true, causes long assertion error messages to be truncated for readability. Setting this to false causes the entire message to be displayed. Defaults to true.

const Code = require('code');
const expect = Code.expect;
const foo = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12];
 
Code.settings.truncateMessages = false;
expect(foo).to.deep.equal([]);

A boolean value that, when false, ignores object prototypes when doing a deep comparison. Defaults to true.

const Code = require('code');
const expect = Code.expect;
const foo = Object.create(null);
 
Code.setting.comparePrototypes = false;
expect(foo).to.deep.equal({});