A framework that makes unit testing your custom elements built with Polymer/lit-element a breeze. This is an alternative to Google Web Component Tester.

Built with Mocha Headless Chrome.

npm install lit-element-tester -g

You may alternatively install the package locally with --save option and use npx utility to run it.

• Development mode with Google Chrome
• Production mode that runs completely headless
• Source map support for debugging
• Code coverage
• HTML fixtures

Take note that Google Chrome is the only supported browser, and there is no plan to add support for other browsers.

lit-element-tester requires you to provide an HTML test runner that will get loaded in Chrome for testing.

Use the following as a template for your test runner: https://github.com/drochgenius/lit-element-tester/blob/master/test/runner.html

We expect this file to be located in a folder called /test at the top level of your project.

Look at the man page.

lit-element-tester -h

You must provide a server configuration file, see here for details. You can add some test-specific configuration in a LitElementTester section.

Example:

"LitElementTester": {
    "instrumentedFiles": ["dist/components/*.js", "dist/mixins/*.js"],
    "testClientContentPath": "test/runner.html",
    "disableLogging": true
}

• instrumentedFiles: an array of globbing patterns to defines the files that need to be instrumented for code coverage.
• testClientContentPath: the path to the HTML test runner.
• disableLogging: set this to true to disable express logging.

lit-element-tester

lit-element-tester -d