empower

empower
================================

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Power Assert feature enhancer for assert function/object.

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

empower 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
---------------------------------------

$3

| return type |
|:-----------------------|
| function or object |

empower function takes function or object(originalAssert) and formatter function created by power-assert-formatter then returns PowerAssert feature added function/object base 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.

#### formatter

| type | default value |
|:-----------|:--------------|
| function | N/A |

formatter function created by power-assert-formatter.

#### options

| type | default value |
|:---------|:--------------|
| object | (return value of empower.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 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.modifyMessageOnRethrow

| type | default value |
|:----------|:--------------|
| boolean | false |

If truthy, modify message property of AssertionError on rethrow.

#### options.saveContextOnRethrow

| type | default value |
|:----------|:--------------|
| boolean | false |

If truthy, add powerAssertContext property to AssertionError on rethrow.

modifyMessageOnRethrow option and saveContextOnRethrow option makes behavior matrix as below.

| modifyMessageOnRethrow | saveContextOnRethrow | resulting behavior |
|:-----------------------|:---------------------|:--------------------------------------------------|
| false (default) | false (default) | Always modify assertion message argument directly |
| true | false | Modify message of AssertionError on fail |
| false | true | Do not modify message of AssertionError but add powerAssertContext property on fail |
| true | true | On fail, modify message of AssertionError and also add powerAssertContext property |

#### options.patterns

| type | default value |
|:--------------------|:--------------------|
| Array of string | objects shown below |

``javascript
[
'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 escallmatch. Any arguments enclosed in bracket (for example, [message]) means optional parameters. Without bracket means mandatory parameters.

$3

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

`javascript
{
destructive: false,
modifyMessageOnRethrow: false,
saveContextOnRethrow: false,
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])'
]
}
`


SUPPORTED ASSERTION LIBRARIES
---------------------------------------
* Node assert API
* Jxck/assert


ASSERTION LIBRARIES KNOWN TO WORK
---------------------------------------
* QUnit.assert
* nodeunit
* buster-assertions


INSTALL
---------------------------------------

$3

Install

$ npm install --save-dev empower


#### use empower npm module on browser

empower function is exported

$3

Install

$ bower install --save-dev empower

Then load (empower` function is exported)

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 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.

[npm-url]: https://npmjs.org/package/empower
[npm-image]: https://badge.fury.io/js/empower.svg

[bower-url]: https://badge.fury.io/bo/empower
[bower-image]: https://badge.fury.io/bo/empower.svg

[travis-url]: https://travis-ci.org/power-assert-js/empower
[travis-image]: https://secure.travis-ci.org/power-assert-js/empower.svg?branch=master

[depstat-url]: https://gemnasium.com/power-assert-js/empower
[depstat-image]: https://gemnasium.com/power-assert-js/empower.svg

[license-url]: https://github.com/power-assert-js/empower/blob/master/MIT-LICENSE.txt
[license-image]: https://img.shields.io/badge/license-MIT-brightgreen.svg?style=flat

[codeclimate-url]: https://codeclimate.com/github/power-assert-js/empower
[codeclimate-image]: https://codeclimate.com/github/power-assert-js/empower/badges/gpa.svg

[coverage-url]: https://coveralls.io/r/power-assert-js/empower?branch=master
[coverage-image]: https://coveralls.io/repos/power-assert-js/empower/badge.svg?branch=master

[gulp-url]: http://gulpjs.com/
[gulp-image]: https://img.shields.io/badge/built_with-gulp-brightgreen.svg