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https://github.com/theKashey/rewiremock
The right way to mock dependencies in Node.js or webpack environment.
https://github.com/theKashey/rewiremock
dependency-injection magic mock mock-library mockery nodejs proxyquire webpack
Last synced: about 1 month ago
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The right way to mock dependencies in Node.js or webpack environment.
- Host: GitHub
- URL: https://github.com/theKashey/rewiremock
- Owner: theKashey
- License: mit
- Created: 2017-05-29T23:26:28.000Z (over 7 years ago)
- Default Branch: master
- Last Pushed: 2023-02-16T22:37:46.000Z (almost 2 years ago)
- Last Synced: 2024-05-19T14:45:23.235Z (7 months ago)
- Topics: dependency-injection, magic, mock, mock-library, mockery, nodejs, proxyquire, webpack
- Language: JavaScript
- Homepage:
- Size: 2.56 MB
- Stars: 482
- Watchers: 5
- Forks: 31
- Open Issues: 49
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
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README
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|__/ \_______/|__/ \__/|__/|__/ \_______/|__/ |__/ \______/ \_______/|__/ \__/
```
[](http://travis-ci.org/theKashey/rewiremock)
[](https://codecov.io/github/thekashey/rewiremock)
[](https://www.npmjs.com/package/rewiremock)
[](https://greenkeeper.io/)
# Quick start
## 1. Install
- `yarn add --dev rewiremock` or `npm i --save-dev rewiremock`
## 2. Setup
I would recommend not importing `rewiremock` directly from tests, but create a `rewiremock.js` file and require it - in this way, you can _preconfigure_ rewiremock for all tests.
### for ts/es6/esm use `import`
```js
// rewiremock.es6.js
import rewiremock from 'rewiremock';
// settings
// ....
rewiremock.overrideEntryPoint(module); // this is important. This command is "transfering" this module parent to rewiremock
export { rewiremock }
```
### for commonjs/nodejs use `require('rewiremock/node')`
```js
// rewiremock.cjs.js
const rewiremock = require('rewiremock/node');
// nothng more than `plugins.node`, but it might change how filename resolution works
/// settings
rewiremock.overrideEntryPoint(module); // this is important
module.exports = rewiremock;
```
### for webpack
```js
// rewiremock.es6.js
import rewiremock from 'rewiremock/webpack';
/// settings
rewiremock.overrideEntryPoint(module); // this is important
export { rewiremock }
```
You will also need to add [a few plugins](https://github.com/theKashey/rewiremock#to-run-inside-webpack-enviroment) to your webpack test configuration (no need to keep them all in production).
> If you import `rewiremock` directly from your tests, you dont need `overrideEntryPoint`
## 3. Use
There are 3 ways to mock, all with pros and cons.
### proxyquire - like
Simplest one.
```js
const file = rewiremock.proxy('file.js', {
'dependency': stub
});
// or
const file = rewiremock.proxy(() => require('file.js'), {
'dependency': stub
});
```
💡to make it really "proxyquire like" - add `.relative` plugin. Which will allow mocking of direct dependencies only, like with `proxyquire`
```js
import rewiremock, { addPlugin, plugins } from 'rewiremock';
addPlugin(plugins.relative);
```
### mockery - like
Most powerfull one
```js
rewiremock('dependency').with(stub);
rewiremock(() => require('dependency')).with(stub);
rewiremock(() => import('dependency')).with(stub); // works with async API only
rewiremock.enable();
const file = require('file.js');
rewiremock.disable();
```
### jest - like
Shortest one
```js
// just place it next to `imports` and add a rewiremock/babel plugin
rewiremock('dependency').with(stub);
```
💡 requires `rewiremock/babel` plugin
## 4. Tune
There are plenty of plugins to make your life easier. For example - this is my favorite setup
```js
import { resolve } from 'path';
import rewiremock, { addPlugin, overrideEntryPoint, plugins } from 'rewiremock';
import { configure } from 'rewiremock/lib/plugins/webpack-alias'; // actually dont use it
configure(resolve(`${__dirname}/../../webpack.config.test.js`));
overrideEntryPoint(module);
// we need webpack aliases
addPlugin(plugins.webpackAlias);
// and all stub names would be a relative
addPlugin(plugins.relative);
// and all stubs should be used. Lets make it default!
addPlugin(plugins.usedByDefault);
export { rewiremock };
```
## What command to use???!!!
```js
// use `require` instead of just the filename to maintain type information
const mock = rewiremock.proxy(() => require('somemodule'), r => {
'dep1': { name: 'override' },
// use all power of rewiremock to mock something as you want...
'dep2': r.with({name: 'override' }).toBeUsed().directChildOnly(), // use all `mocking API`
}));
```
There are two important things here:
- You can use `require` or `import` to specify the file to require and the file to mock. This helps to __resolve file names__ and maintain type information(if you have it). See `Guided Mocking` below.
- You can mix simplified helpers (like `.proxy`) and the main API.
### ESM modules
If you want to support ESM modules(powered by [@std/ESM](https://github.com/standard-things/esm/), not _native_ modules) you have to use the `import` function.
- use `.module` - an "async" version of `.proxy`
```js
const mock = await rewiremock.module(() => import('somemodule'), {...});
```
- or just use `import` - that would
```
rewiremock(() => require('xxx').with({});
rewiremock('yyy').with({});
const file = await import('somemodule');
```
Ok! Let's move forward!
# API
## main API
- `rewiremock.enable()` - wipes cache and enables interceptor.
- `rewiremock.disable()` - wipes cache and disables interceptor.
- `rewiremock.around(loader, creator):Promise< T >` - loads a module in an **asynchronous** sandbox.
- `rewiremock.proxy(file, stubs):T` - _proxyquire_ like mocking api, where file is file name, and stubs are an object or a function.
- `rewiremock.module(loader, stubs):Promise< T >` - async version of proxy, where loader is a function.
## mocking API
- `rewiremock(moduleName: string)` - fabric for a moduleNames's mock
- `rewiremock(moduleImport: loader)` - async fabric for a module import function.
- `.enable/disable()` - to enable or disable mock (enabled by default).
- `.with(stubs: function | Object)` - overloads module with a value
- `.withDefault(stub: function | Object)` - overload `default` es6 export
- `.es6()` - marks module as ES6( __esModule )
- `.by(otherModule: string| function)` - overload by another module(if string provider) or by result of a function call.
- `.callThrough()` - first load the original module, and next extend it by provided stub.
- `.mockThrough([stubFactory])` - first load the original module, and then replaces all exports by stubs.
- `.dynamic()` - enables hot mock updates.
- `.toBeUsed()` - enables usage checking.
- `.directChildOnly` - will do mock only direct dependencies.
- `.calledFromMock` - will do mock only dependencies of mocked dependencies.
- `rewiremock.getMock(moduleName: string|loader)` - returns existing mock (_rewiremock(moduleName)_ will _override_)
## isolation API
- `rewiremock.isolation()` - enables isolation
- `rewiremock.withoutIsolation()` - disables isolation
- `rewiremock.passBy(pattern or function)` - enables some modules to pass throught isolation.
## sandboxing
- `rewiremock.inScope(callback)` - place synchronous callback inside a sandbox.
## helper functions
- `rewiremock.stubFactory(factory)` - define a stub factory for mockThrough command.
### Automocking
Rewiremock supports (inspired by [Jest](https://facebook.github.io/jest/docs/en/manual-mocks.html)) auto `__mocks__`ing.
Just create `__mocks__/fileName.js`, and `fileName.js` will be replaced by the mock. Please refer to Jest documentation for use cases.
If you don't want a particular file to be replaced by its mock - you can disable it with:
```js
rewiremock('fileName.js').disable();
```
# Which API to use?
Yep - there are 4 top-level ways to activate a mock - `inScope`, `around`, `proxy` or just `enable`.
### A common way to mock.
Rewiremock provides lots of APIs to help you set up mocks, and get the mocked module.
- If everything is simple - use __rewiremock.proxy__. (~proxyquire)
- If you have issues with name resolve - use __rewiremock.module__ and resolve names by yourself.
- If you need scope isolation - use __rewiremock.around__, or inScope.
- If you need advanced syntax and type checking - use __rewiremock.around__.
- You always can just use __.enable/.disable__ (~ mockery).
> All the mocks await you to provide "stubs" to override the real implementation.
> If you want just to ensure you have called endpoints – use rewiremock('someFile').mockThrough.
# Usage
- `proxy` will load a file by its own ( keep in mind - name resolution is a complex thing)
```js
const mock = rewiremock.proxy('somemodule', (r) => ({
'dep1': { name: 'override' },
'dep2': r.with({name: 'override' }).toBeUsed().directChildOnly(), // use all `mocking API`
'dep3': r.mockThrough() // automatically create a test double
}));
```
- you can require a file by yourself. ( yep, proxy is a "god" function)
```js
const mock = rewiremock.proxy(() => require('somemodule'), {
'dep1': { name: 'override' },
'dep2': { onlyDump: 'stubs' }
}));
```
- or use es6 `import` (not for Node.js mjs `real` es6 modules)
`module` is an async version of proxy, so you can use imports
```js
const mock = await rewiremock.module(() => import('somemodule'), {
'dep1': { name: 'override' },
'dep2': { onlyDump: 'stubs' }
}));
```
- `around` - another version of .module, where you can do just ~anything~.
```js
const mock = await rewiremock.around(() => import('somemodule'), () => {
rewiremock('dep1').with('something');
callMom();
// prepare mocking behavior
}));
```
- `enable`/`disable` - Low level API
```js
rewiremock('someThing').with('someThingElse')
rewiremock.enable();
// require something
rewiremock.disable();
```
In all the cases you can specify what exactly you want to mock, or just mock anything
```js
addPlugin(plugins.mockThroughByDefault);
```
# Hoisted mocking
You can also use a top-level mocking, the same as Jest could only provide
```js
import sinon from 'sinon';
import rewiremock from 'rewiremock';
import Component1 from 'common/Component1';
import selectors from 'common/selectors';
rewiremock('common/Component1').by('common/Component2');
rewiremock('common/Component2/action').with({ action: () => {} });
rewiremock('common/selectors').mockThrough(() => sinon.stub());
selectors.findUser.returns("cat"); // this is sinon stub.
```
As result Component1 will be replaced by Component2, action with empty function and
all selectors by sinon stubs, with one configured.
This is only possible via babel plugin, and without it, this code will be executed without any sense, as long mocking
will be configured after the files required.
### Limitations
- Other babel plugins, including JSX, won't work inside webpack _hoisted_ code. But you may define
any _specific_ code in "functions", and let JavaScript hoist it.
- Most variables, that you have defined in the file, are not visible to __hoisted__ code, as long they are __not yet defined__.
Only functions will be hoisted.
1. Add `rewiremock/babel` into the plugin section of your `.babelrc` or `babel.config.js` file
```js
// .babelrc
{
"presets": [
//.....
],
"plugins": [
"rewiremock/babel"
]
}
```
2. This example will be transpiled into
```js
import sinon from 'sinon';
import rewiremock from 'rewiremock';
rewiremock('common/Component1').by('common/Component2');
rewiremock('common/Component2/action').with({ action: () => {} });
rewiremock('common/selectors').mockThrough(() => sinon.stub());
rewiremock.enabled();
import Component1 from 'common/Component1';
import selectors from 'common/selectors';
rewiremock.disable();
selectors.findUser.returns("cat"); // this is sinon stub.
```
Keep in mind - rewiremock will hoist mock definition next to rewiremock import.
- You can __use__ anything __above__ rewiremock import
- You can __mock__ anything __below__ rewiremock import
### Changing the mocks after the mocking
It is possible to partially change mocking already being applied.
```js
rewiremock('./foo')
.callThrough()
.with({ action1: action1Stub1 })
.dynamic();
const foo = require('./foo');
foo.action == action1Stub1;
rewiremock.getMock('./foo')
.with({ action1: action1Stub2 });
//while will RESET the mock, and could not change existing ones.
rewiremock('./foo')
.with({ action1: action1Stub2 });
foo.action == action1Stub2;
rewiremock('./foo')
.with({ });
foo.action == theRealFoo;
```
#### Changing the hoisted mocks
```js
import rewiremock from 'rewiremock';
import foo from './foo';
rewiremock('./foo')
.with({ action1: action1Stub1 })
.dynamic();
const fooMock = rewiremock.getMock('./foo');
describe(..., () => {
it('...', () => {
fooMock.with({ });
// while may NOT found the mock
rewiremock.getMock('./foo').with({ });
});
})
```
### Guided mocking
You may use `require` or `import` to let IDE help you to properly write fileName,
and hide all filename resolution and transformation behind the scenes.
But there are things you have to keep in mind
1. Resolution of synchronous API happens on .enable
```js
rewiremock(() => require('./fileToMock1')); // this mock would work
rewiremock.enable();
rewiremock(() => require('./fileToMock2')); //this mock WOULD NOT WORK!
```
2. Using async API will throw an error
```js
rewiremock(() => import('./fileToMock1'));
rewiremock.enable(); // this is an exception
```
3. Async API requires async API
```js
rewiremock.module( () => import('file')) // this is ok
rewiremock.around(..., rw => rw.mock(() => import('file2'))) // this is ok
```
# Type safety
Rewiremock can provide type-safe mocks. To enable type-safety to follow these steps:
1. Use TypeScript or Flow.
2. Use dynamic import syntax.
3. Use `rewiremock.around` or `rewiremock.module` to perform a mock.
4. Use the async form of rewiremock mock declaration.
```js
// @flow
import rewiremock from 'rewiremock';
rewiremock.around(
() => import('./a.js'),
mock => {
mock(() => import('./b.js'))
.withDefault(() => "4")
.with({testB: () => 10})
.nonStrict() // turn off type system
.with({ absolutely: "anything" })
}
);
```
If default export is not exists on module 'b', or there is no named export testB, or types do not match - type system will throw.
If you will declare an async mock, it will not be resolved by the time of execution - Rewiremock will throw on Error.
If you have async imports inside a mocked file, follow this syntax
```js
rewiremock.around(
() => import('./a.js'),
mock => {
// just before loader function rewiremock enabled itself
mock(() => import('./b.js').then(mock=>mock)) // mocks `live` one `tick` more
// just after loader function resolved rewiremock disables itself
mock => {
....
}
}
);
```
# Type safety for JavaScript
Rewiremock can check mock against the real implementation. This does not perform `type checking`, but
could check exported names and exported types (function vs number, for example).
Rewiremock expects that mock will be __less or equal__ than the original file.
```text
rewiremock: mocked export "somethingMissing" does not exist in ./b.js
rewiremock: exported type mismatch: ./b.js:default. Expected function, got number
```
To activate exports comparison
```js
rewiremock('somemoduname')
.toMatchOrigin(); // to activate
// or
import rewiremock, { addPlugin, removePlugin, plugins } from 'rewiremock';
addPlugin(plugins.alwaysMatchOrigin);
```
# Setup
## To run with Node.js
Just use it. You can also activate node.js, which will double-check all modules names on a real FS, but...
everything might work out of the box.
> PS: Just use `usedByDefault` to ensure module names are resolved correctly.
There is also a special entry point for node.js, with nodejs plugin activated, and rewiremock as es5 export
```js
const rewiremock = require('rewiremock/node');
// meanwhile
const rewiremock = require('rewiremock').default;
```
## To run inside webpack environment.
Rewiremock can `emulate` few webpack features(like aliases) in node.js environment, but it also can be run inside webpack.
> Actually rewiremock is the first client-side mocking library
But not so fast, handy. First, you have to have 3(!) Plugins enabled.
1. `webpack.NamedModulesPlugin()`. To enlight the real names of modules, not "numbers". __Enabled by default__ in webpack "dev" mode
2. `webpack.HotModuleReplacementPlugin()`. To provide some information about connections between modules.
Might be (and usually) __already enabled__, double activation of this plugin might break everything.
3. `rewiremock.webpackPlugin`. To add some magic and make gears rolling.
```js
plugins: [
new webpack.NamedModulesPlugin(),
new webpack.HotModuleReplacementPlugin(),
new (require("rewiremock/webpack/plugin"))()
]
```
That's all. Now all magic will happen at the client-side.
> It is better to use .proxy/module command with direct require/import and leaves all names conversion to webpack.
#### Hint
For better dev experience include special configuration of webpack
```js
import rewiremock from 'rewiremock/webpack';
```
### webpack troubleshooting
Currently, there are 2 known problems, both for mocha+webpack, ie using node.js to run webpack bundle:
- TypeError: Cannot read property 'webpackHotUpdate' of undefined
Caused by babel. Just don't use babel then running webpack bundles (ie babel-register). Use babel to create bundles.
- TypeError: Cannot read property 'call' of undefined
Caused by webpack. Sometimes it does not include some important files.
To solve this problem just `import('rewiremock/webpack/interceptor')` in scaffolding.
The problem is simply - this file does not exist in the bundle.
## To actually... mock
First - define your mocks. You can do it in any place, this is just a setup.
```javascript
import rewiremock from 'rewiremock';
...
// totaly mock `fs` with your stub
rewiremock('fs')
.with({
readFile: yourFunction
});
// replace path, by other module
rewiremock('path')
.by('path-mock');
// replace enzyme by preconfigured one (from https://medium.com/airbnb-engineering/unlocking-test-performance-migrating-from-mocha-to-jest-2796c508ec50)
rewiremock('enzyme')
.by(({requireActual}) => {
// see rest of possible params in d.ts file
const enzyme = requireActual('enzyme');
if (!mockSetup) {
const chai = requireActual('chai');
const chaiEnzyme = requireActual('chai-enzyme');
chai.use(chaiEnzyme());
}
return enzyme;
});
// replace default export of ES6 module
rewiremock('reactComponent')
.withDefault(MockedComponent)
// replace only part of some library and keep the rest
rewiremock('someLibrary')
.callThrough()
.with({
onlyOneMethod
})
// secure yourself and from 'unexpected' mocks
rewiremock('myDep')
.with(mockedDep)
.calledFromMock()
```
# Running
There is a simply way to do it: Just enable it, and dont forget to disable it later.
```javascript
//in mocha tests
beforeEach( () => rewiremock.enable() );
//...
// here you will get some advantage in type casting and autocompleting.
// it will actually works...
const someModule = require('someModule');
//...
afterEach( () => rewiremock.disable() );
```
Once enabled, rewiremock will wipe all mocked modules from cache, and all modules which require them.
Including your test.
Once disabled it will restore everything.
All unrelated to test dependencies will be kept. Node modules, react, common files - everything.
As a result - it will run faster.
# inScope
Sometimes you will have independent tests in a single file, and you might need separate mocks for each one.
`inScope` execute callback inside a sandbox, and all mocks or plugins or anything else you have added will not leaks away.
```javascript
rewiremock.inScope( () => {
rewiremock('something').with(something);
rewiremock.enable();
// is 'something' mocked? Yes
....
rewiremock.disable();
// is 'something' mocked? No
// is it still listed as mock? Yes
});
// is 'something' mocked or listed? No
```
# Around
And there is a bit harder way to do it - scope.
inScope will create a new internal scope, next you can add something new to it, and then it will be destroyed.
It will also enable/disable rewiremock just in time.
This helps keep tests in isolation.
PS: scopes are nesting each other as javascript prototypes do.
```javascript
rewiremock.around(
() => import('somemodule'), // load a module. Using import or require.
// just before it you can specify mocks or anything else
(mock) => {
addPlugin(nodePlugin);
mock('./lib/a/foo').with(() => 'aa');
mock('./lib/a/../b/bar').with(() => 'bb');
mock('./lib/a/../b/baz').with(() => 'cc');
}
) // at this point scope is dead
.then((mockedBaz) => {
expect(mockedBaz()).to.be.equal('aabbcc');
});
```
or just
```javascript
rewiremock.around(() => import('somemodule')).then(mockedModule => doSomething)
```
or
```javascript
rewiremock.around(
() => import('somemodule').then( mockedModule => doSomething),
(mock) => aPromise
);
```
Currently, `.inScope` is the only API capable to handle es6(not node [m]js!) dynamic imports.
# Proxy
Sometimes it is much easier to combine all the things.
```js
// preferred way - create stubs using a function, where R is mock creator
rewiremock.proxy('somemodule', (r) => ({
'dep1': { name: 'override' },
'dep2': r.with({name: 'override' }).toBeUsed().directChildOnly() // same powerfull syntax
}));
// straight way - just provide stubs.
rewiremock.proxy('somemodule', {
'dep1': { name: 'override' },
'dep2': { name: 'override' }
}));
```
# Plugins
By default - rewiremock has limited features. You can extend its behavior via plugins.
- `relative`. A bit simplistic, proxyquire-like behavior. Will override only first level dependencies, and will wipe a lot of modules from a cache. If you need override at other place - use `.atAnyPlace` modificator.
- `nodejs`. Common support to "usual" Node.js application. Will absolutize all paths. Will wipe cache very accurately.
- `webpack-alias`. __deprecated__. Enables you to use webpack aliases as module names. Please [use node-js resolution](https://github.com/theKashey/rewiremock/issues/7#issuecomment-621666559) for this.
- `childOnly`. Only first level dependencies will be mocked.
- `protectNodeModules`. Ensures that any module from node_modules will not be wiped from a cache.
- `toBeUsed`. Adds feature. The only plugin enabled by default.
- `disabledByDefault`. All mocks will be disabled on create and at the end of each cycle.
- `mockThroughByDefault`. All mocks mocked through.
- `usedByDefault`. All mocks to be used by the fact (reverse isolation)
```javascript
import rewiremock, { addPlugin, removePlugin, plugins } from 'rewiremock';
addPlugin(plugins.webpackAlias);
removePlugin(plugins.webpackAlias);
```
# Nested declarations
If you import rewiremock from another place, for example, to add some defaults mocks - it will not gonna work.
Each instance of rewiremock in independent.
You have to pass your instance of rewiremock to build a library.
PS: note, rewiremock did have nested API, but it was removed.
# Isolation
Unit testing requires all dependencies to be mocked. All!
To enable it, run
```javascript
rewiremock.isolation();
//or
rewiremock.withoutIsolation();
```
Then active - rewiremock will throw error on require of any unknown module.
The unknown is a module which is nor mocked, nor marked as pass-through.
To make few modules to be `invisible` to rewiremock, run
```javascript
rewiremock.passBy(/*pattern or function*/);
rewiremock.passBy(/common/);
rewiremock.passBy(/React/);
rewiremock.passBy(/node_modules/);
rewiremock.passBy((name) => name.indexOf('.node')>=0 )
```
# Reverse isolation
Sometimes you have to be sure, that you mock was called.
Isolation will protect you then you add new dependencies, `.toBeUsed` protect you from removal.
# Jest
Jest is a very popular testing framework, but it has one issue - is already contain mocking support.
> Do not use rewiremock and jest. Even if it is possible.
## Jest will not allow ANY other mocking library to coexists with Jest
To use rewiremock with Jest add to the beginning of your file
```js
// better to disable auto mock
jest.disableAutomock();
// Jest breaks the rules, and you have to restore nesting of modules.
rewiremock.overrideEntryPoint(module);
// There is no way to use overload by Jest require or requireActual.
// use the version provided by rewiremock.
require = rewiremock.requireActual;
```
!!! the last line here may disable Jest sandboxing. !!!
Also, it will disable Jest transformation, killing all the jest magics.
To be able to continue using ES6/imports - you have to enforce Babel to be applied in the `common` way.
```js
describe('block of tests', () => {
// require babel-register in describe or it block.
// NOT! On top level. Jest sandboxing and isolation are still in action,
// and will reset all settings to default
require("babel-register");
})
```
PS: Jest will set BABEL_ENV to `test`.
It is better just to use `rewiremock.requireActual`, without overriding global require.
# Your own setup.
In most cases you have to:
- add plugin
- setup default passBy rules
- add some common mocks
- do something else.
And it is not a good idea to do it in every test you have.
It is better to have one setup file, which will do everything for you
* Part 1 - man in the middle
```javascript
// this is your test file
// instead of importing original file - import your own one
// import rewiremock from 'rewiremock';
import rewiremock from 'test/rewiremock';
```
* Part 2 - create your own one
```javascript
// this tests/rewiremock.js
import rewiremock, { addPlugin, overrideEntryPoint} from 'rewiremock';
// do anything you need
addPlugin(something);
rewiremock('somemodule').with(/*....*/);
// but don't forget to add some magic
overrideEntryPoint(module); // <-- set yourself as top module
// PS: rewiremock will wipe this module from cache to keep magic alive.
export default rewiremock;
```
* Part 3 - enjoy.
You extract some common code into a helper. And things become a lot easier.
# Default configuration
Absolutely the same - preconfiguring rewiremock one can achieve via default configuration.
Just put __rewiremock.config.js__ in the root dir, next to project.json, and export a configuration function
```js
// rewiremock.config.js
import wrongrewiremock, {plugins} from 'rewiremock';
export default rewiremock => {
// do everything with "right" rewiremock
rewiremock.addPlugin(plugins.nodejs)
}
```
# Caching
Default cache policy follows these steps:
1. Preparation:
- all files required from the original test, while interceptor is active, will bypass cache.
- all files you indicate as mocks will be removed from the cache.
- all "soiled" files which rely on mocks - will also be removed from the cache.
- repeat.
2. Finalization
- repeat all mocks and possible "soiled" by mocks files.
- copy over the old cache.
- or restore the old cache completely if `forceCacheClear` mode is set.
The last variant is the default for proxyquire and mockery, also it is more "secure" from different side effects.
Regardless, default is the first variant - as a way faster, and secure enough.
As a result of this mocking strategy, you can mock any file at any level, while keeping other files cached.
#### Hint
If you __don't want__ this - just add `relative` plugin. It will allow mocking only for modules
> _required from __module__ with __parent__ equals __entryPoint__._
PS: module with parent equals entryPoint - any module you require from the test (it is an entry point).
required from that module - the first level required. Simple.
# Own plugins
Don't forget - you can write your own plugins.
plugin is an object with fields:
```javascript
{
// to transform name. Used by alias or node.js module
fileNameTransformer: (fileName, parentModule) => fileName;
// check should you wipe module or not. Never used :)
wipeCheck: (stubs, moduleName) => boolean,
// check is mocking allowed for a module. User in relative plugin
shouldMock: (mock, requestFilename, parentModule, entryPoint) => boolean
}
```
# Extensions
Rewiremock will automatically try to resolve file
- by specified name
- adding .js, .jsx, .ts, .tsx, .mjs
- you can override defaults
```js
import {resolveExtensions} from 'rewiremock';
resolveExtensions(['.wasm', '.mjs', '.js', '.json']);
```
`resolveExtensions` is quite similar to [webpack's resolve extensions](https://webpack.js.org/configuration/resolve/#resolve-extensions).
# Not working?
If something is not working - just check that you:
- added a plugin to transform names (Node.js, webpackAlias or relative)
- use .toBeUsed for each mocks
And they were mocked. If not - rewiremock will throw an Error.
# Goal
- give the ability to mock everything - CommonJS, ES6, inside Node.js or webpack.
- give the ability to do correctly - isolation, type checking, powerful API
- give the ability to do it easy - simple API to cover all the cases.
# Other libraries
Dependency mocking, inspired by the best libraries:
- [mockery](https://github.com/mfncooper/mockery) - `rewiremock` __is__ a better `mockery`, with the same interface.
- [proxyquire](https://github.com/theKashey/proxyquire) - `rewiremock` __is__ a better `proxyquire`, with the same interface.
- [mock-require](https://github.com/boblauer/mock-require) - things must not be complex, `rewiremock` __is__ not.
- [jest.mocks](https://facebook.github.io/jest/docs/en/manual-mocks.html) - `jest` is awesome. As well as `rewiremock`.
Rewiremock is a better version of your favorite mocking library. It can be used with `mocha`, `ava`, `karma`, and anything that's not `jest`.
By design, rewiremock has the same behavior as Mockery. But it can behave like other libraries too, exposing handy interfaces to make mocking a joy. Supports type-safe mocking and provides TS/Flow types for itself.
# Wanna read something about?
[Rewiremock - medium article](https://medium.com/@antonkorzunov/how-to-mock-dependency-in-a-node-js-and-why-2ad4386f6587)
[all by tag](https://medium.com/tag/rewiremock/latest)
# Licence
MIT
Happy mocking!