inject-loader

library4.0.1jsnpmunverified

A Webpack loader for injecting mock dependencies into modules under test. Current stable version 4.0.1, maintained steadily. It wraps all require statements in a module so you can substitute them during testing. Unlike proxyquire or rewire, it works as a Webpack inline loader, making it seamless in Webpack-based projects. Supports Webpack 1 through 4. Particularly useful for unit testing where you need to mock internal dependencies of a module before it executes.

testing

npm install inject-loader

github ↗package ↗

INSTALL

IMPORT

SIG · INJECT-LOADER

inject-loader

testingjavascriptv4.0.1

Install

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Import

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Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

inject-loader

✓ import MyModuleInjector from 'inject-loader!./MyModule';

✗ const inject = require('inject-loader'); const MyModuleInjector = inject('./MyModule');

inject-loader is used as an inline Webpack loader, not a regular module. The correct usage is to prefix the module path with 'inject-loader!' in the require/import statement.

inject-loader (CommonJS)

✓ const MyModuleInjector = require('inject-loader!./MyModule');

✗ const MyModuleInjector = require('inject-loader')( './MyModule' );

When using CommonJS, still use the inline loader syntax in the require path.

injector function

✓ const MyModule = MyModuleInjector({ 'lib/dispatcher': DispatcherMock, 'events': EventsMock, 'lib/handle_action': HandleActionMock });

✗ const MyModule = MyModuleInjector.inject({ 'lib/dispatcher': DispatcherMock });

The loader returns a function that accepts an object mapping dependency paths to mock modules.

Shows how to require a module via inject-loader inline and inject mock dependencies.

// Example test using inject-loader with Jest const MyModuleInjector = require('inject-loader!./MyModule'); const DispatcherMock = { register: jest.fn() }; const EventsMock = { EventEmitter: jest.fn() }; const HandleActionMock = jest.fn(); const MyModule = MyModuleInjector({ 'lib/dispatcher': DispatcherMock, 'events': EventsMock, 'lib/handle_action': HandleActionMock }); // Now MyModule uses the mocked dependencies DispatcherMock.register.mock.calls.length; // 1

Debug

Known issues

gotchaYou must use the inline loader syntax 'inject-loader!./module' in your require/import statements. Using inject-loader as a regular module and calling it as a function will not work.

fix

Use 'require("inject-loader!./module")' instead of 'require("inject-loader").(./module)'.

affects: >=4.0

deprecatedWebpack 1 and 2 support is deprecated. The loader still works but no longer actively tested.

fix

Upgrade to Webpack 3 or 4 for official support.

affects: >=4.0

gotchaThe loader wraps all require statements by default. If you want to exclude certain dependencies, you must provide flags (not documented in readme).

fix

Check loader options or use flags as described in the example folder: require('inject-loader?exclude=events!./module').

affects: >=4.0

breakingIn v4, the loader now returns a single injector function instead of an object with inject method.

fix

Call the result directly: const module = require('inject-loader!./module')({...}) instead of require('inject-loader!./module').inject({...}).

affects: >=4.0

Errors

Common errors & fixes

TypeError: inject_loader is not a function

Using inject-loader as a regular module instead of an inline loader.

fix

Use require('inject-loader!./MyModule') instead of require('inject-loader')(...).

Module not found: Error: Can't resolve 'inject-loader'

inject-loader not installed or not in node_modules.

fix

Run 'npm install --save-dev inject-loader'.

Critical dependency: require function is used in a way in which dependencies cannot be statically extracted

Webpack 4 warns about dynamic requires; inject-loader uses dynamic require internally.

fix

This warning is expected and usually harmless. Suppress with webpack config stats: 'warningsFilter: /Critical dependency/'.

Inject loader only works with CommonJS modules (module.exports/require).

Using ES module syntax (import/export) in the injected module.

fix

Ensure the module under test uses CommonJS require/module.exports, or use a babel transform to convert.

Upgrade

Version history

4.0.1latest on npm

Audit

Dependencies

webpackrequiredpeer dependency required to function as a Webpack loader

Agent activity

11 hits · last 30 days

node

Resources

githubhttps://github.com/plasticine/inject-loader ↗

packagehttps://www.npmjs.com/package/inject-loader ↗