Using Cockpit test VMs with your own test framework

The Cockpit Starter Kit provides the scaffolding for your own Cockpit extensions: a simple page (in React), build system (webpack, babel, eslint, etc.), and an integration test using Cockpit’s own Python test API on top of the Chromium DevTools Protocol. See the recent introduction for details.

But in some cases you want to use a different testing framework; perhaps you have an already existing project and tests. Then it is convenient and recommended to still using Cockpit’s test VM images: they provide an easy way to test your project on various Fedora/Red Hat/Debian/Ubuntu flavors; and they take quite a lot of effort to maintain! Quite fortunately, using the test images is not tightly bound to using Cockpit’s test API, and not even to tests being written Python. They can be built and used entirely through command line tools from Cockpit’s bots/ directory, so you can use those with any programming language and test framework.

Building and interacting with a test VM

To illustrate this, let’s check out the Starter Kit and build a CentOS 7 based VM with cockpit and the starter kit installed:

$ git clone
$ cd starter-kit
$ make vm

Ordinarily, the generated test/images/centos-7.qcow2 would be used by test/check-starter-kit. But let’s tinker around with the VM image manually. Cockpit’s module for using these VMs can be used as a command line program:

$ bots/machine/ centos-7
ssh -o ControlPath=/tmp/ssh-%h-%p-%r-23253 -p 2201 root@

It takes a few seconds to boot the VM, then it prints three lines:

  • The SSH command to run something inside the VM
  • The URL for the forwarded Cockpit port 9090
  • A constant RUNNING flag that test suites can poll for to know when to proceed.

You can now open that URL in your browser to log into Cockpit (user “admin”, password “foobar”) and see the installed Starter Kit page, or run a command in the VM through the given SSH command:

$ ssh -o ControlPath=/tmp/ssh-%h-%p-%r-23253 -p 2202 root@ head -n2 /etc/os-release
NAME="CentOS Linux"
VERSION="7 (Core)"

The VM gets shut down once the process gets a SIGTERM (useful for test suites) or SIGINT (useful for just pressing Control-C when interactively starting this in a shell).

Using in your test suite

Let’s use the above in a Puppeteer test. check-puppeteer.js is a straight port of check-starter-kit; of course it is a little longer than the original as we don’t have the convenience functions of to automatically start and tear down VMs or do actions like “log into Cockpit”, but it is still fairly comprehensible. Download it into the tests/ directory of your starter-kit checkout, then install puppeteer:

$ PUPPETEER_SKIP_CHROMIUM_DOWNLOAD=1 npm install puppeteer@0.12.0

This will avoid downloading an entire private copy of chromium-browser and use the system-installed one. (Of course you can also just call npm install puppeteer if you don’t care about the overhead). Now run the tests:

$ DEBUG="puppeteer:page,puppeteer:frame" PYTHONPATH=bots/machine test/check-puppeteer.js

This will run them in a verbose mode where you can follow the browser queries and events.

Let’s walk through some of the code:

function startVm() {
    return new Promise((resolve, reject) => {
        let proc = child_process.spawn("bots/machine/", [testOS], { stdio: ["pipe", "pipe", "inherit"] });
        let buf = "";
        proc.stdout.on("data", data => {
            buf += data.toString();
            if (buf.indexOf("\nRUNNING\n") > 0) {
                let lines = buf.split("\n");
                resolve({ proc: proc, ssh: lines[0], cockpit: lines[1] });
        proc.on("error", err => { throw `Failed to start vm-run: ${err}` });

This uses as above to launch the VM. In a “real” test suite this would go into the per-test setup code. check-puppeteer.js does not use any test case organization framework (like jest or QUnit), but if you have more than two or three test cases it’s recommended to use one.

async function testStarterKit() {
    const vm = await startVm();

    const browser = await puppeteer.launch(
        // disable sandboxing to also work in docker
        { headless: true, executablePath: 'chromium-browser', args: [ "--no-sandbox" ] });

This is the actual test case. Here we start Puppeteer, and here you can change various options to influence the test. For example, set headless: false to get a visible Chomium window and follow live what the test does (or where it hangs).

    const page = await browser.newPage();

    try {
        // log in
        await page.goto(vm.cockpit);
        await page.type('#login-user-input', 'admin');
        await page.type('#login-password-input', 'foobar');

This is the equivalent of Cockpit test’s Browser.login_and_go(). In a real test you would probably factorize this into a helper function.

        await page.waitFor('#host-nav a[title="Starter Kit"]');
        await page.goto(vm.cockpit + "/starter-kit");
        let frame = getFrame(page, 'cockpit1:localhost/starter-kit');

        // verify expected heading
        await frame.waitFor('.container-fluid h2');
        await frame.waitForFunction(() => document.querySelector(".container-fluid h2").innerHTML == "Starter Kit");

        // verify expected host name
        let hostname = vmExecute(vm, "cat /etc/hostname").trim();
        await frame.waitFor('.container-fluid span');
        await frame.waitForFunction(
            h => document.querySelector(".container-fluid span").innerHTML == ("Running on " + h),
            {}, hostname);

This is a direct translation of what check-starter-kit does: Assert the expected heading and host name message.

    catch (err) {
        const attachments = process.env["TEST_ATTACHMENTS"];
        if (attachments) {
            console.error("Test failed, taking screenshot...");
            await page.screenshot({ path: attachments + "/testStarterKit-FAIL.png"});
        throw err;

This part is optional, but very useful for debugging failed tests. If any assertion fails, this creates a PNG screenshot from the current browser page state. Run the test with TEST_ATTACHMENTS=/some/existing/directory to enable this. The Cockpit CI machinery will export any files in this directory to the http browsable test results directory.

     finally {
        await browser.close();

This is a poor man’s “test teardown” which closes the browser and VM.


starter-kit and external Cockpit project tests are still fairly new, so there are for sure things that could work more robustly, easier, more flexibly, or just have better documentation. If you run into trouble, please don’t hesitate telling us about it, preferably by filing an issue.

Happy hacking!

The Cockpit Development Team