jest-webpack-alias
Preprocessor for Jest that is able to resolve require()
statements using webpack aliases.
See also transform-jest-deps.
:warning:
Consider using babel-plugin-module-resolver for new projects instead of jest-webpack-alias
. An example setup can be seen at the Next.js repo.
Install
npm install --save-dev jest-webpack-alias
Setup
File __tests__/preprocessor.js
:
var babelJest = require('babel-jest');
require('babel-register');
var webpackAlias = require('jest-webpack-alias');
module.exports = {
process: function(src, filename) {
if (filename.indexOf('node_modules') === -1) {
src = babelJest.process(src, filename);
src = webpackAlias.process(src, filename);
}
return src;
}
};
File package.json
:
{
...
"jest": {
...
"scriptPreprocessor": "<rootDir>/__tests__/preprocessor.js",
},
"jest-webpack-alias": {
"profile": "dev"
}
}
Common problems
Importing CSS and SCSS files
In order to use statements like require('some-styles.css')
in a testing environment, it's best to use an npm module like ignore-styles to ignore files that match certain file extensions in require()
statements.
Manual package resolution
Code like this will not work, because an AST parser is not smart enough to evaluate variables into strings.
var moduleName = 'myModName';
var computed = require(moduleName);
It can be rewritten like this, using the resolve
function:
var resolve = require('jest-webpack-alias').resolve;
var moduleName = 'myModName';
var computed = require(resolve(moduleName, __filename));
package.json options
-
jest-webpack-alias.configFile
: Optional, default is "webpack.config.js"
. If provided, this should be a path
fragment relative to your package.json
file. Example: "webpack/config.dev.js"
.
-
jest-webpack-alias.profile
: Optional. If provided, will expect your webpack config to be an array of profiles, and
will match against the name
field of each to choose a webpack config that applies to your Jest tests. See
https://github.com/webpack/webpack/tree/master/examples/multi-compiler for an example of this kind of setup.
Known issues
resolve.modulesDirectories
only searches the directory containing your package.json file, not all ancestors of current file
License
MIT