empower-core

What is empower-core?

The empower-core npm package is a core library for power-assert, which provides a way to enhance assertion libraries by adding descriptive assertion messages. It is designed to work with various assertion libraries to provide more informative error messages, making it easier to debug test failures.

What are empower-core's main functionalities?

Enhanced Assertion Messages

This feature allows you to enhance the standard assertion messages with more descriptive information. In the example, the assertion `enhancedAssert(result === 5, 'Expected result to be 5')` will provide a more detailed error message if the assertion fails.

const assert = require('assert');
const empower = require('empower-core');
const enhancedAssert = empower(assert);

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

const result = add(2, 2);
enhancedAssert(result === 5, 'Expected result to be 5');

Customizable Assertion Formatting

This feature allows you to customize the formatting of assertion messages. By providing patterns, you can control how the assertion messages are displayed. In the example, the pattern `['assert(value, [message])']` is used to format the assertion message.

const assert = require('assert');
const empower = require('empower-core');
const enhancedAssert = empower(assert, { patterns: ['assert(value, [message])'] });

function multiply(a, b) {
  return a * b;
}

const result = multiply(3, 3);
enhancedAssert(result === 10, 'Expected result to be 10');

Other packages similar to empower-core

power-assert

Power-assert is a similar package that provides descriptive assertion messages. It is designed to work with various assertion libraries and offers a more user-friendly way to debug test failures. Compared to empower-core, power-assert is a more comprehensive solution that includes additional features and integrations.

chai

Chai is a popular assertion library for Node.js and the browser that provides a variety of assertion styles (BDD, TDD, and assert). While it does not specifically focus on enhancing assertion messages like empower-core, it offers a rich set of features for writing tests and assertions.

should

Should is another assertion library for Node.js that provides a fluent interface for writing assertions. It focuses on readability and expressiveness, making it easier to write and understand tests. While it does not offer the same level of enhanced assertion messages as empower-core, it provides a user-friendly way to write assertions.

README

empower-core

Power Assert feature enhancer for assert function/object.

DESCRIPTION

empower-core is a core module of power-assert family. empower-core enhances standard assert function or any assert-like object to work with power-assert feature added code instrumented by espower.

empower-core works with standard assert function (best fit with Mocha), and also supports assert-like objects/functions provided by various testing frameworks such as QUnit, buster.js, and nodeunit.

Pull-requests, issue reports and patches are always welcomed. See power-assert project for more documentation.

CHANGELOG

See CHANGELOG

API

var enhancedAssert = empowerCore(originalAssert, [options])

return type
function or object

empower-core function takes function or object(originalAssert) then returns PowerAssert feature added function/object based on originalAssert. If destructive option is falsy, originalAssert will be unchanged. If destructive option is truthy, originalAssert will be manipulated directly and returned enhancedAssert will be the same instance of originalAssert.

originalAssert

type	default value
function or object	N/A

originalAssert is an instance of standard assert function or any assert-like object. see SUPPORTED ASSERTION LIBRARIES and ASSERTION LIBRARIES KNOWN TO WORK section. Be careful that originalAssert will be manipulated directly if destructive option is truthy.

options

type	default value
object	(return value of empowerCore.defaultOptions())

Configuration options. If not passed, default options will be used.

options.destructive

type	default value
boolean	false

If truthy, modify originalAssert destructively.

If false, empower-core mimics originalAssert as new object/function, so originalAssert will not be changed. If true, originalAssert will be manipulated directly and returned enhancedAssert will be the same instance of originalAssert.

options.bindReceiver

type	default value
boolean	true

bindReceiver defaults to true, meaning assertion methods have their this value bound to the original assertion. Setting bindReceiver to false causes the this reference to be passed through from the actual invocation.

options.onError

options.onSuccess

type	default value
function	(function defined in empowerCore.defaultOptions())

Both methods are called with a single event argument, it will have the following properties:

• event.enhanced - true for methods matching patterns. false for methods matching wrapOnlyPatterns.

• event.originalMessage - The actual value the user provided for optional message parameter. This will be undefined if the user did not provide a value, even if the underlying assertion provides a default message.

• event.defaultMessage - If you use objects instead of strings to specify patterns (see below), the defaultMessage metadata will be copied directly on the event object.

• event.matcherSpec - This contains the complete parsed matcher spec as supplied, as well as any additional metadata you may have supplied (see patterns section below for details on how to supply additional metadata).

• event.args - An array of the actual arguments passed to the assertion.

• event.assertionThrew - Whether or not the underlying assertion threw an error. This will always be true in an onError callback, and always false in an onSuccess callback.

• event.error - Only present if event.assertionThrew === true. Contains the error thrown by the underlying assertion method.

• event.returnValue - Only present if event.assertionThrew === false. Contains the value return value returned by the underlying assertion method.

• event.powerAssertContext - Only present for methods that match patterns, and only in code that has been enhanced with the power-assert transform. It contains the information necessary for power-assert renderers to generate their output. Implementors of onError should usually attach it to the error object

  function onError (errorEvent) {
    var e = errorEvent.error;
    if (errorEvent.powerAssertContext && /^AssertionError/.test(e.name)) {
        e.powerAssertContext = errorEvent.powerAssertContext;
    }
    throw e;
  }
  

options.modifyMessageBeforeAssert

type	default value
function	N/A

TBD

options.patterns

type	default value
Array of string or objects	objects shown below

[
    'assert(value, [message])',
    'assert.ok(value, [message])',
    'assert.equal(actual, expected, [message])',
    'assert.notEqual(actual, expected, [message])',
    'assert.strictEqual(actual, expected, [message])',
    'assert.notStrictEqual(actual, expected, [message])',
    'assert.deepEqual(actual, expected, [message])',
    'assert.notDeepEqual(actual, expected, [message])',
    'assert.deepStrictEqual(actual, expected, [message])',
    'assert.notDeepStrictEqual(actual, expected, [message])'
]

Target patterns for power assert feature instrumentation.

Pattern detection is done by call-signature. Any arguments enclosed in bracket (for example, [message]) means optional parameters. Without bracket means mandatory parameters.

Instead of a string, you may alternatively specify an object with a pattern property, and any other arbitrary data. Currently only defaultMessage is formally recommended, but you can attach any data here and it will be passed to the onSuccess and onError handlers.

[
  {
    pattern: 'assert.fail([message])',
    defaultMessage:'assert.fail() was called!!'
  },
  ...
]

options.wrapOnlyPatterns

type	default value
Array of string	empty array

Methods matching these patterns will not be instrumented by the code transform, but they will be wrapped at runtime and trigger events in the onSuccess and onError callbacks. Note that "wrap only" events will never have a powerAssertContext property.

Similar to the options.patterns, you may supply objects with a pattern member, and the additional metadata will be passed to the assertion listeners.

var options = empowerCore.defaultOptions();

Returns default options object for empowerCore function. In other words, returns

{
    destructive: false,
    onError: onError,
    onSuccess: onSuccess,
    patterns: [
        'assert(value, [message])',
        'assert.ok(value, [message])',
        'assert.equal(actual, expected, [message])',
        'assert.notEqual(actual, expected, [message])',
        'assert.strictEqual(actual, expected, [message])',
        'assert.notStrictEqual(actual, expected, [message])',
        'assert.deepEqual(actual, expected, [message])',
        'assert.notDeepEqual(actual, expected, [message])',
        'assert.deepStrictEqual(actual, expected, [message])',
        'assert.notDeepStrictEqual(actual, expected, [message])'
    ]
}

with sensible default for onError and onSuccess

function onError (errorEvent) {
    var e = errorEvent.error;
    if (errorEvent.powerAssertContext && e.name === 'AssertionError') {
        e.powerAssertContext = errorEvent.powerAssertContext;
    }
    throw e;
}

function onSuccess(successEvent) {
    return successEvent.returnValue;
}

SUPPORTED ASSERTION LIBRARIES

• Node assert API

ASSERTION LIBRARIES KNOWN TO WORK

• QUnit.assert
• nodeunit
• buster-assertions

INSTALL

via npm

Install

$ npm install --save-dev empower-core

use empower-core npm module on browser

empowerCore function is exported

<script type="text/javascript" src="./path/to/node_modules/empower-core/build/empower-core.js"></script>

via bower

Install

$ bower install --save-dev empower-core

Then load (empowerCore function is exported)

<script type="text/javascript" src="./path/to/bower_components/empower-core/build/empower-core.js"></script>

OUR SUPPORT POLICY

We support Node under maintenance. In other words, we stop supporting old Node version when their maintenance ends.

We also support "modern enough" browsers such as Chrome, Firefox, Safari, Edge etc.

Any other environments are not supported officially (means that we do not test against them on CI service). empower-core is known to work with old browsers, and trying to keep them working though.

AUTHOR

• Takuto Wada

CONTRIBUTORS

• James Talmage (jamestalmage)

LICENSE

Licensed under the MIT license.