The empower npm package is a tool designed to enhance assertion libraries by providing more detailed and readable assertion error messages. It works by instrumenting assertion functions to capture additional context and information about the assertions being made.
Enhanced Assertion Messages
This feature allows you to use enhanced assertion messages that provide more context and detail about the assertion failure, making it easier to debug.
const assert = require('assert');
const empower = require('empower');
const enhancedAssert = empower(assert);
try {
enhancedAssert.equal(1, 2);
} catch (e) {
console.log(e.message); // Outputs detailed assertion error message
}Integration with Various Assertion Libraries
Empower can be integrated with various assertion libraries, allowing you to enhance the error messages of your existing assertions without changing your testing framework.
const assert = require('assert');
const empower = require('empower');
const enhancedAssert = empower(assert);
try {
enhancedAssert.deepEqual({ a: 1 }, { a: 2 });
} catch (e) {
console.log(e.message); // Outputs detailed assertion error message
}Customizable Output
You can customize the output of the enhanced assertion messages by configuring empower with different patterns and options.
const assert = require('assert');
const empower = require('empower');
const enhancedAssert = empower(assert, { patterns: ['assert.*'] });
try {
enhancedAssert.equal(1, 2);
} catch (e) {
console.log(e.message); // Outputs detailed assertion error message
}Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any javascript testing framework. Unlike empower, Chai provides a rich set of assertion styles and plugins, but it does not focus specifically on enhancing error messages.
Should is an expressive, readable, and powerful assertion library for node. It extends the Object prototype with a single non-enumerable getter that allows you to express assertions in a natural language style. While it provides readable assertions, it does not focus on enhancing error messages like empower.
Expect is a minimalistic assertion library that works well with Jest. It provides a set of assertion functions and is designed to work seamlessly with Jest's test runner. Unlike empower, it does not focus on enhancing error messages but provides a simple and straightforward API for assertions.
Power Assert feature enhancer for assert function/object.
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.
See CHANGELOG
| 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.
| 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.
| type | default value |
|---|---|
function | N/A |
formatter function created by power-assert-formatter.
| type | default value |
|---|---|
object | (return value of empower.defaultOptions()) |
Configuration options. If not passed, default options will be used.
| 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.
| type | default value |
|---|---|
boolean | false |
If truthy, modify message property of AssertionError on rethrow.
| 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 |
| type | default value |
|---|---|
Array of string | 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 escallmatch. Any arguments enclosed in bracket (for example, [message]) means optional parameters. Without bracket means mandatory parameters.
Returns default options object for empower function. In other words, returns
{
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])'
]
}
Install
$ npm install --save-dev empower
empower function is exported
<script type="text/javascript" src="./path/to/node_modules/empower/build/empower.js"></script>
Install
$ bower install --save-dev empower
Then load (empower function is exported)
<script type="text/javascript" src="./path/to/bower_components/empower/build/empower.js"></script>
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.
Licensed under the MIT license.
FAQs
Power Assert feature enhancer for assert function/object
The npm package empower receives a total of 117,954 weekly downloads. As such, empower popularity was classified as popular.
We found that empower demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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