Home > @rushstack/webpack-plugin-utilities > Testing > getTestingWebpackCompilerAsync

Testing.getTestingWebpackCompilerAsync() function

This function generates a webpack compiler with default configuration and the output filesystem mapped to a memory filesystem. This is useful for testing webpack plugins/loaders where we do not need to write to disk (which can be costly).

Signature:

export declare function getTestingWebpackCompilerAsync(entry: string, additionalConfig?: Configuration, memFs?: IFs): Promise<(Stats | MultiStats) | undefined>;

Parameters

Parameter	Type	Description
entry	string	The entry point for the webpack compiler
additionalConfig	Configuration	(Optional) Any additional configuration that should be merged with the default configuration
memFs	IFs	(Optional) The memory filesystem to use for the output filesystem. Use this option if you want to _inspect_, analyze, or read the output files generated by the webpack compiler. If you do not need to do this, you can omit this parameter and the output files.

Returns:

Promise<(Stats | MultiStats) | undefined>

• A webpack compiler with the output filesystem mapped to a memory filesystem

Remarks

If you want to be able to read, analyze, access the files written to the memory filesystem, you can pass in a memory filesystem instance to the memFs parameter.

Example 1

import Testing from '@rushstack/webpack-plugin-utilities';

describe('MyPlugin', () => {
  it('should run', async () => {
    const stats = await Testing.getTestingWebpackCompiler(
      `./src/index.ts`,
    );

    expect(stats).toBeDefined();
 });
});

Example 2

import Testing from '@rushstack/webpack-plugin-utilities';
import { createFsFromVolume, Volume, IFs } from 'memfs';
import path from 'path';

describe('MyPlugin', () => {
 it('should run', async () => {
   const virtualFileSystem: IFs = createFsFromVolume(new Volume());
   const stats = await Testing.getTestingWebpackCompiler(
     `./src/index.ts`,
     {},
     virtualFileSystem
   );

   expect(stats).toBeDefined();
   expect(virtualFileSystem.existsSync(path.join(__dirname, 'dist', 'index.js'))).toBe(true);
 });
});