Performance test example: performance of click event in the inspector

Let’s look at a trivial but practical example and add a simple test to measure the performance of a click in the inspector.

First we create a file under tests/inspector since we are writing an inspector test. We call the file click.js.

We will use a dummy test document here: data:text/html,click test document.

We prepare the imports needed to write the test, from head.js and inspector-helper.js:

• testSetup, testTeardown, openToolbox and runTest from head.js

• reloadInspectorAndLog from inspector-helper.js

The full code for the test looks as follows:

const {
  reloadInspectorAndLog,
} = require("devtools/docs/tests/inspector-helpers");

const {
  openToolbox,
  runTest,
  testSetup,
  testTeardown,
} = require("devtools/docs/head");

module.exports = async function() {
  // Define here your custom document via a data URI:
  const url = "data:text/html,click test document";

  await testSetup(url);
  const toolbox = await openToolbox("inspector");

  const inspector = toolbox.getPanel("inspector");
  const window = inspector.panelWin; // Get inspector's panel window object
  const body = window.document.body;

  await new Promise(resolve => {
    const test = runTest("inspector.click");
    body.addEventListener("click", function () {
      test.done();
      resolve();
    }, { once: true });
    body.click();
  });

  // Check if the inspector reload is impacted by click
  await reloadInspectorAndLog("click", toolbox);

  await testTeardown();
}

Finally we add an entry in damp-tests.js:

  {
    name: "inspector.click",
    path: "inspector/click.js",
    description:
      "Measure the time to click in the inspector, and reload the inspector",
  },

Since this is an inspector test, we add it under TEST_SUITES.INSPECTOR, which contains all the tests which will run with the damp-inspector test suite in continuous integration. The test is still part of the overall damp suite by default, there is no action needed to ensure that.

Then we can run our test with:

./mach talos-test --suite damp --subtest inspector.click