Content Browser Test Tips

A random collection of useful things to know when writing browser tests.

Executing JavaScript

If the test needs to use the return value of the script, use EvalJs():

  // Works with numerical types...
  EXPECT_EQ(0, EvalJs(shell(), "1 * 0");

  // ... string types ...
  EXPECT_EQ("BODY", EvalJs(shell(), "document.body.tagName");

  // and booleans too. Note the explicit use of EXPECT_EQ() instead of
  // EXPECT_TRUE() or EXPECT_FALSE(); this is intentional, and the latter
  // will not compile.
  EXPECT_EQ(false, EvalJs(shell(), "2 + 2 == 5"));

Like many other test helpers (e.g. the navigation helpers), the first argument accepts RenderFrameHost, WebContents, and other types.

  // Executes in the main frame.
  EXPECT_EQ(true, EvalJs(shell()->GetWebContents(), "window.top == window"));

  // Also executes in the main frame.
  EXPECT_EQ(true, EvalJs(shell(), "window.top == window"));

  // Executes in the first child frame of the main frame.
  EXPECT_EQ(
      false,
      EvalJs(ChildFrameAt(shell()->GetWebContents()->GetMainFrame(), 0),
             "window.top == window"));

Otherwise, simply use ExecJs():

  EXPECT_TRUE(ExecJs("console.log('Hello world!')"));

Note that these helpers block until the script completes. For async execution, use ExecuteScriptAsync().

Finally, JsReplace() provides a convenient way to build strings for script execution:

  EXPECT_EQ("00", EvalJs(JsReplace("$1 + $2", 0, "0")));

Cross-origin navigations

For cross-origin navigations, it is to simplest to configure all hostnames to resolve to 127.0.0.1 in tests, using a snippet like this:

  void SetUpOnMainThread() override {
    host_resolver()->AddRule("*", "127.0.0.1");
    ASSERT_TRUE(embedded_test_server()->Start());
  }

After that, EmbeddedTestServer::GetURL() can be used to generate navigable URLs with the specific origin:

  const GURL& url_a = embedded_test_server()->GetURL("a.com", "/title1.html");
  const GURL& url_b = embedded_test_server()->GetURL("b.com", "/empty.html");

Most test resources are located in //content/test/data, e.g. navigating to GetURL("a.com", "/title1.html") will serve //content/test/data/title1.html as the content.

Browser-initiated navigation to a specific origin

Note: using arbitrary hostnames requires the host resolver to be correctly configured.

NavigateToURL() begins and waits for the navigation to complete, as if the navigation was browser-initiated, e.g. from the omnibox:

  GURL url(embedded_test_server()->GetURL("a.com", "/title1.html"));
  EXPECT_TRUE(NavigateToURL(shell(), url));

Note: NavigateToURL() allows subframes to be targetted, but outside of history navigations, subframe navigations are generally renderer-initiated.

Renderer-initiated navigation to a specific origin

Note: using arbitrary hostnames requires the host resolver to be correctly configured.

NavigateToURLFromRenderer() begins and waits for the navigation to complete, as if the navigation was renderer-initiated, e.g. by setting window.location:

  // Navigates the main frame.
  GURL url_1(embedded_test_server()->GetURL("a.com", "/title1.html"));
  EXPECT_TRUE(NavigateToURLFromRenderer(shell()->GetWebContents(), url_1));

  // Navigates the main frame too.
  GURL url_2(embedded_test_server()->GetURL("b.com", "/page_with_iframe.html"));
  EXPECT_TRUE(NavigateToURLFromRenderer(shell()->GetWebContents(), url_2));

  // Navigates the first child frame.
  GURL url_3(embedded_test_server()->GetURL("a.com", "/empty.html"));
  EXPECT_TRUE(
      NavigateToURLFromRenderer(
          ChildFrameAt(shell()->GetWebContents()->GetMainFrame(), 0),
          url_3));

Dynamically generating a page with iframes

Note: using arbitrary hostnames requires the host resolver to be correctly configured.

cross_site_iframe_factory.html is a helper that makes it easy to generate a page with an arbitrary frame tree by navigating to a URL. The query string to the URL allows configuration of the frame tree, the origin of each frame, and a number of other options:

  GURL url(embedded_test_server()->GetURL(
      "a.com", "/cross_site_iframe_factory.html?a(b(a),c,example.com)"));
  EXPECT_TRUE(NavigateToURL(shell(), url));

Will generate a page with:

Main frame with origin `a.com`
  ├─ Child frame #1 with origin `b.com`
  │    └─ Grandchild frame with origin `a.com`
  ├─ Child frame #2 with origin `c.com`
  └─ Child frame #3 with origin `example.com`

Embedding an <iframe> with a specific origin

Note: using arbitrary hostnames requires the host resolver to be correctly configured.

Sometimes, a test page may need to embed a cross-origin URL. This is problematic for pages that contain only static HTML, as the embedded test server runs on a randomly selected port. Instead, static HTML can use the cross-site redirector to generate a cross-origin frame:

<!-- static_iframe.html -->
<html>
  <body>
    <iframe src="/cross-site/b.com/title1.html">
  </body>
</iframe>

Important: the cross-site redirector is not enabled by default. Override SetUpOnMainThread() to configure it like this:

  void SetUpOnMainThread() override {
    ...
    SetupCrossSiteRedirector(embedded_test_server());
    ...
  }

Simulating a slow load

Navigates to a page that takes 60 seconds to load.

  GURL url(embedded_test_server()->GetURL("/slow?60");
  EXPECT_TRUE(NavigateToURL(shell(), url));

The embedded test server also registers other default handlers that may be useful.