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Testing Extensions#

Renderer Process Unit Testing#

UI components in the extension's renderer process are based on React/ReactDOM. These components can be tested by popular React testing tools like React Testing Library.

If you are using the Yeoman Lens Extension Generator to scaffold extension project then the testing environment for render process is already set up for you. Just use npm start or yarn test to run the tests.

For example, I have a component GlobalPageMenuIcon and want to test if props.navigate is called when user clicks the icon.

My component GlobalPageMenuIcon

import React from "react"
import { Renderer } from "@k8slens/extensions";

const {
  Component: {
} = Renderer;

const GlobalPageMenuIcon = ({ navigate }: { navigate?: () => void }): JSX.Element => (
    onClick={() => navigate()}

The test

import React from "react"
import { render, screen, fireEvent } from "@testing-library/react";

import GlobalPageMenuIcon from "./GlobalPageMenuIcon";

test("click called navigate()", () => {
    const navigate = jest.fn();
    render(<GlobalPageMenuIcon navigate={navigate} />);"global-page-menu-icon"));

In the example we used React Testing Library but any React testing framework can be used to test renderer process UI components.

There are more example tests in the generator's template. Extend your tests based on the examples.

Main Process Unit Testing#

Code in the extension's main process consists of normal JavaScript files that have access to extension api, you can write unit tests using any testing framework.

If you are using the Yeoman Lens Extension Generator to scaffold your extension project then the Jest testing environment is set up for you. Just use npm start or yarn test to run the tests.



Extension developers might find console.log() useful for printing out information and errors from extensions. To use console.log(), note that Lens is based on Electron, and that Electron has two types of processes: Main and Renderer.

Renderer Process Logs#

In the Renderer process, console.log() is printed in the Console in Developer Tools (View > Toggle Developer Tools).

Main Process Logs#

Viewing the logs from the Main process is a little trickier, since they cannot be printed using Developer Tools.


On macOS, view the Main process logs by running Lens from the terminal:


You can also use to view the Main process logs.


On Linux, you can access the Main process logs using the Lens PID. First get the PID:

ps aux | grep Lens | grep -v grep

Then get the Main process logs using the PID:

tail -f /proc/[pid]/fd/1 # stdout (console.log)
tail -f /proc/[pid]/fd/2 # stdout (console.error)