当浏览器窗口重叠时，并行运行Selenium测试失败

Question

我正在使用以下代码（取自 Setting up your own test automation environment ）

var webdriver = require('selenium-webdriver'),
    By = webdriver.By,
    until = webdriver.until;

var driver_fx = new webdriver.Builder()
    .forBrowser('firefox')
    .usingServer('http://localhost:4444/wd/hub')
    .build();

var driver_chr = new webdriver.Builder()
    .forBrowser('chrome')
    .usingServer('http://localhost:4444/wd/hub')
    .build();

searchTest(driver_fx);
searchTest(driver_chr);

function searchTest(driver) {
  driver.get('http://www.google.com');
  driver.findElement(By.name('q')).sendKeys('webdriver');

  driver.sleep(1000).then(function() {
    driver.findElement(By.name('q')).sendKeys(webdriver.Key.TAB);
  });

  driver.findElement(By.name('btnK')).click();

  driver.sleep(2000).then(function() {
    driver.getTitle().then(function(title) {
      if(title === 'webdriver - Google Search') {
        console.log('Test passed');
      } else {
        console.log('Test failed');
      }
      driver.quit();
    });
  });


}

它应该打开firefox和chrome，转到谷歌，在输入中输入一些文本，单击搜索按钮，然后检查窗口标题。

我使用以下命令运行selenium服务器：

java -Dwebdriver.gecko.driver=/home/sean/bin/geckodriver -Dwebdriver.chrome.driver=/home/sean/bin/chromedriver -jar ~/Downloads/selenium-server-standalone-3.14.0.jar

然后node index.js进行测试。这会打开firefox和chrome并出现此错误：

WebDriverError: Element <input name="btnK" type="submit"> is not clickable at point (564,411) because another element <div class="sbqs_c"> obscures it
Build info: version: '3.14.0', revision: 'aacccce0', time: '2018-08-02T20:13:22.693Z'
System info: host: 'mx', ip: '127.0.0.1', os.name: 'Linux', os.arch: 'amd64', os.version: '4.13.0-46-generic', java.version: '1.8.0_171'
Driver info: driver.version: unknown
    at Object.checkLegacyResponse (/home/sean/workspace/selenium-test/node_modules/selenium-webdriver/lib/error.js:546:15)
    at parseHttpResponse (/home/sean/workspace/selenium-test/node_modules/selenium-webdriver/lib/http.js:509:13)
    at doSend.then.response (/home/sean/workspace/selenium-test/node_modules/selenium-webdriver/lib/http.js:441:30)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:118:7)
From: Task: WebElement.click()
    at thenableWebDriverProxy.schedule (/home/sean/workspace/selenium-test/node_modules/selenium-webdriver/lib/webdriver.js:807:17)
    at WebElementPromise.schedule_ (/home/sean/workspace/selenium-test/node_modules/selenium-webdriver/lib/webdriver.js:2010:25)
    at WebElementPromise.click (/home/sean/workspace/selenium-test/node_modules/selenium-webdriver/lib/webdriver.js:2092:17)
    at searchTest (/home/sean/workspace/selenium-test/index.js:58:39)
    at Object.<anonymous> (/home/sean/workspace/selenium-test/index.js:47:1)
    at Module._compile (module.js:649:30)
    at Object.Module._extensions..js (module.js:660:10)
    at Module.load (module.js:561:32)
    at tryModuleLoad (module.js:501:12)
    at Function.Module._load (module.js:493:3)

如果我一次在1个浏览器中运行测试，它们都会通过。

我尝试不使用selenium服务器并让selenium-webdriver模块处理启动进程。还尝试启动具有多个节点的集线器（在同一台机器中）并在不同节点中运行每个浏览器。都有同样的错误。

我是否理解，如果我的测试有click（）之类的操作，那么在同一物理/虚拟机中一次只能打开一个浏览器实例（相同的webdriver或不同的webdriver），以避免浏览器窗口相互重叠？

什么是最佳做法？每个selenium节点有1个docker，每个节点设置maxSession 1？只打开一个浏览器并在那里运行所有测试？

是否存在没有此约束的测试自动化工具？

编辑：使用第三方服务，如browserstack和saucelabs不是一个选项