Jest-erb-transformer NPM

Jest ERB Transformer

Overview

Custom transformer for compiling Embedded Ruby template files (.erb) for use in the Jest JavaScript testing framework.

Install

Add to project using your package manager, e.g. yarn:

yarn add jest-erb-transformer --dev

Configuration

Jest Configuration

Ensure the "erb" file extension and the jest-erb-transformer extension matcher and configuration is included in the project's package.json jest key:

"moduleFileExtensions": [
  "js",
  "erb"
],

"transform": {
  "^.+\\.erb$": "jest-erb-transformer"
}

See the Jest docs for more information on the configuration of transformers.

Options

To add custom configuration, such as using the Ruby on Rails runner for ERB compilation, add a configuration object to the transformer entry in the project package.json using the Jest transformer configuration syntax. For example, to compile in the rails environment:

"transform": {
  "^.+\\.erb$": [ "jest-erb-transformer", { "application": "rails" } ]
}

Babel

By default the transformer does not process its output with Babel.

To perform post-processing with Babel, either configure the transformer babelConfig option as outlined in the options table below, or I have found including the .erb files in the babel-jest transformer directly has worked in some scenarios. For example:

"transform": {
  "^.+\\.js(?:\\.erb)?$": "babel-jest",
  "^.+\\.erb$": [ "jest-erb-transformer", { "application": "rails" } ]
  }

All Options

Key	Default Value	Description
`"application"`	`"ruby"`	Transformer is run using `ruby` by default, set value to `"rails"` to use `bin/rails runner`. The `"rails"` option can be useful if the .erb files include Ruby on Rails specific environment variables such as `Rails.application.credentials`.
`"engine"`	`"erb"`	Transformer uses the ruby 'ERB' engine by default, to use the Erubi engine set the value to `"erubi"`.
`"timeout"`	`"5000"`	Set the timeout duration in milliseconds for the compilation of individual files.
`"babelConfig"`	`false`	Process the output of the ERB transformer using babel-jest. Options: `false` - Disables the use of Babel.`true` - Babel processing using project or file-relative Babel configuration file.`./path/to/.babelrc.json` - Relative path to Babel configuration file to be used for processing.`{ "comments": false }` - Object containing Babel options to be used for processing.