Front End testing with Selenium

The test

You can run Selenium steps to involve your front-end applications in the end-to-end test. Selenium step consists of two parts - selenium test and Catcher’s catcher_modules.frontend.selenium() step definition which will trigger it.

Selenium step can look like:

- selenium:
        file: resources/
        libraries: '/usr/share/java/*'
file argument should point to your Selenium test. Catcher currently support JavaScript, Python, Java, Kotlin and Jar-files (in case you already prepared tests and don’t need to compile them every time you run the step).
This example will run your Java-based Selenium test. In case of Java/Kotlin it will try to compile it using provided libraries argument.

Java source file looks like:

package selenium;

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.firefox.FirefoxDriver;

public class MySeleniumTest {

    public static void main(String[] args) {
        WebDriver driver = new FirefoxDriver();
        try {
            WebElement element = driver.findElement("q"));
        } finally {

It will go to google and search by “Cheese!” string. Catcher’s step will pass if Selenium test passes.

Variables and output

Catcher pushes it’s context variables to Selenium steps as environment variables, so you can access them from tests. For example:

    site_url: ''
    - selenium:
            driver: '/usr/lib/geckodriver'
            file: resources/test.js
        register: {title: '{{ OUTPUT.title }}'}
    - echo: {from: '{{ title }}', to: variable.output}

Here Catcher’s context has site_url variable which is accessible within JavaScript (for other languages similarly). As well as page’s title is accessible for Catcher as an output variable.


const {Builder, By, Key, until} = require('selenium-webdriver');
    async function basicExample(){
        let driver = await new Builder().forBrowser('firefox').build();
            await driver.get(process.env.site_url);
            await driver.findElement('q')).sendKeys('webdriver', Key.RETURN);
            await driver.wait(until.titleContains('webdriver'), 1000);
            await driver.getTitle().then(function(title) {
                        console.log('{\"title\":\"' + title + '\"}')
        catch(err) {
            process.exitCode = 1;

To output any value simply use stdout. In case of Json you can access fields directly (f.e. OUTPUT.title json output). If Catcher fails to parse json - it will use the whole output as a plain text.

Libraries and Dependencies

Catcher dockerfile comes with nodeJS, Java1.8, Kotlin and Python Selenium libraries installed, as well as Firefox, Chrome and Opera drivers.

To run Selenium steps locally you need all dependencies, libraries and drivers be installed in your system. Driver should be included in your PATH or passed as a driver argument.
In case of Java/Kotlin scr compilation you should have javac/kotlinc installed in your system.
In case of jar files running - java should be installed.
In case of JavaScript - nodeJs should be installed.