fune/browser/base/content/test/referrer/browser_referrer_middle_click.js

// Tests referrer on middle-click navigation.
// Middle-clicks on the link, which opens it in a new tab.

function startMiddleClickTestCase(aTestNumber) {
  info(
    "browser_referrer_middle_click: " + getReferrerTestDescription(aTestNumber)
  );
  someTabLoaded(gTestWindow).then(function (aNewTab) {
    BrowserTestUtils.switchTab(gTestWindow.gBrowser, aNewTab).then(() => {
      checkReferrerAndStartNextTest(
        aTestNumber,
        null,
        aNewTab,
        startMiddleClickTestCase
      );
    });
  });

  clickTheLink(gTestWindow, "testlink", { button: 1 });
}

function test() {
  requestLongerTimeout(10); // slowwww shutdown on e10s
  startReferrerTest(startMiddleClickTestCase);
}