PHPUnit + Selenium：如何处理页面之间的移动

Question

一旦我的测试尝试从一页移动到另一页，我真的很难弄清楚如何阻止 PHPUnit+Selenium 中断。例如，我做这样的事情：

public function myTest()
{
    $this->clickOnElement('somelink');
    $this->assertEquals('content', $this->byId('newElement'));
}

当我尝试运行它时，我收到如下错误：

1) myTestClass::myTest
PHPUnit_Extensions_Selenium2TestCase_WebDriverException: Element not found in the cache
   - perhaps the page has changed since it was looked up
Command duration or timeout: 107 milliseconds

只有在两个页面之间移动时才会出现问题，并且您要查找的元素在两个页面上都存在（如标题或标题）。这里实际上有两个问题，都是竞争条件：

1. clickOnElement() 开始加载下一页，但在此之前byId() 在当前页面 上运行并找到该元素。然后浏览器完成加载新页面，assertContains() 尝试从元素中获取值。但是新页面现在已经加载，我们拥有的元素引用来自 previous 页面。由于该元素不再存在于当前 DOM 中，因此您会收到有关过时元素的错误。

2. clickOnElement() 开始加载下一页，但在加载完成之前byId() 在新的但未完全加载的页面上运行。由于页面尚未完成加载，您会收到“未找到元素”错误。

任何想法如何解决这两个问题？

Answer 1

好的，我想我想通了。第二个问题（在页面加载之前寻找元素）可以通过设置implicitWait() 值来解决：

public function setUpPage()
{
    // If an element cannot be found because the page is still loading, keep
    // trying for 5000ms before failing
    $this->timeouts()->implicitWait(5000);
}

每个测试只需要调用一次，所以把它放在setUpPage() 是一个好地方。这将导致 Selenium 在抱怨找不到给定元素之前继续查找长达 5 秒钟。 5 秒应该是足够的时间来完成页面加载和元素变得可访问。

第一个问题（等到浏览器离开当前页面）需要对测试代码进行一些更改才能正常工作。首先，我们创建一个名为 waitForURLChange() 的新函数，然后在下面的示例中，每当我们希望浏览器导航到新 URL 时，我们都会调用它。

private $urlPrevious;
/// Wait for the browser URL to change.  Must be called once before the test starts
/// to read in the initial URL.
public function waitForURLChange()
{
    if (!empty($this->urlPrevious)) {
        $prev = $this->urlPrevious; // workaround for PHP limitation with $this and closures
        $this->waitUntil(
            function($testCase) use ($prev) {
                return strcmp($testCase->url(), $prev) ? 1 : null;
            },
            2000 // milliseconds to wait before giving up if the URL hasn't changed
        );
    }

    // Make sure the URL has actually changed (in case of timeout above)
    $this->assertNotEquals($this->urlPrevious, $this->url());

    $this->urlPrevious = $this->url();
}

现在在您的测试代码中，您只需在每个导致页面转换的操作之后调用waitForURLChange()：

public function myTest()
{
    // Call the function once first to read in the current URL.  This does not wait.  You
    // could put this in setUpPage() instead so you don't need it at the start of every test.
    $this->waitForURLChange();

    // Do something that causes the browser to move to a different page.
    $this->clickOnElement('somelink');

    // Call the function again, and it won't return until the browser has started
    // loading the new page.
    $this->waitForURLChange();

    // Now perform the test, knowing the page may not have fully loaded yet but you are
    // definitely not stuck on the previous page.
    $this->assertEquals('content', $this->byId('newElement'));

    // Click the back button in the browser (for example).
    $this->back();

    // Wait until we're back at the previous page.
    $this->waitForURLChange();

    // ...and so on...
}