MockMvc and WebDriver

In the previous sections, we have seen how to use MockMvc in conjunction with the raw HtmlUnit APIs. In this section, we use additional abstractions within the Selenium WebDriver to make things even easier.

Why WebDriver and MockMvc?

We can already use HtmlUnit and MockMvc, so why would we want to use WebDriver? The Selenium WebDriver provides a very elegant API that lets us easily organize our code. To better show how it works, we explore an example in this section.

Despite being a part of Selenium, WebDriver does not require a Selenium Server to run your tests.

Suppose we need to ensure that a message is created properly. The tests involve finding the HTML form input elements, filling them out, and making various assertions.

This approach results in numerous separate tests because we want to test error conditions as well. For example, we want to ensure that we get an error if we fill out only part of the form. If we fill out the entire form, the newly created message should be displayed afterwards.

If one of the fields were named “summary”, we might have something that resembles the following repeated in multiple places within our tests:

Java

HtmlTextInput summaryInput = currentPage.getHtmlElementById("summary");
summaryInput.setValueAttribute(summary);

So what happens if we change the id to smmry? Doing so would force us to update all of our tests to incorporate this change. This violates the DRY principle, so we should ideally extract this code into its own method, as follows:

Java

public HtmlPage createMessage(HtmlPage currentPage, String summary, String text) {
	setSummary(currentPage, summary);
	// ...
}

public void setSummary(HtmlPage currentPage, String summary) {
	HtmlTextInput summaryInput = currentPage.getHtmlElementById("summary");
	summaryInput.setValueAttribute(summary);
}

Doing so ensures that we do not have to update all of our tests if we change the UI.

We might even take this a step further and place this logic within an Object that represents the HtmlPage we are currently on, as the following example shows:

Java

public class CreateMessagePage {

  final HtmlPage currentPage;

  final HtmlTextInput summaryInput;

  final HtmlSubmitInput submit;

  public CreateMessagePage(HtmlPage currentPage) {
    this.currentPage = currentPage;
    this.summaryInput = currentPage.getHtmlElementById("summary");
    this.submit = currentPage.getHtmlElementById("submit");
  }

  public <T> T createMessage(String summary, String text) throws Exception {
    setSummary(summary);

    HtmlPage result = submit.click();
    boolean error = CreateMessagePage.at(result);

    return (T) (error ? new CreateMessagePage(result) : new ViewMessagePage(result));
  }

  public void setSummary(String summary) throws Exception {
    summaryInput.setValueAttribute(summary);
  }

  public static boolean at(HtmlPage page) {
    return "Create Message".equals(page.getTitleText());
  }
}

Formerly, this pattern was known as the Page Object Pattern. While we can certainly do this with HtmlUnit, WebDriver provides some tools that we explore in the following sections to make this pattern much easier to implement.

MockMvc and WebDriver Setup

To use Selenium WebDriver with the Web MVC Test framework, make sure that your project includes a test dependency on org.seleniumhq.selenium:selenium-htmlunit3-driver.

We can easily create a Selenium WebDriver that integrates with MockMvc by using the MockMvcHtmlUnitDriverBuilder as the following example shows:

Java

WebDriver driver;

@BeforeEach
void setup(WebApplicationContext context) {
  driver = MockMvcHtmlUnitDriverBuilder
      .webAppContextSetup(context)
      .build();
}

This is a simple example of using MockMvcHtmlUnitDriverBuilder. For more advanced usage, see Advanced MockMvcHtmlUnitDriverBuilder.

The preceding example ensures that any URL that references localhost as the server is directed to our MockMvc instance without the need for a real HTTP connection. Any other URL is requested by using a network connection, as normal. This lets us easily test the use of CDNs.

MockMvc and WebDriver Usage

Now we can use WebDriver as we normally would but without the need to deploy our application to a Servlet container. For example, we can request the view to create a message with the following:

Java

CreateMessagePage page = CreateMessagePage.to(driver);

We can then fill out the form and submit it to create a message, as follows:

Java

ViewMessagePage viewMessagePage =
    page.createMessage(ViewMessagePage.class, expectedSummary, expectedText);

This improves on the design of our HtmlUnit test by leveraging the Page Object Pattern. As we mentioned in Why WebDriver and MockMvc?, we can use the Page Object Pattern with HtmlUnit, but it is much easier with WebDriver. Consider the following CreateMessagePage implementation:

public class CreateMessagePage extends AbstractPage { (1)

  (2)
  private WebElement summary;
  private WebElement text;

  @FindBy(css = "input[type=submit]") (3)
  private WebElement submit;

  public CreateMessagePage(WebDriver driver) {
    super(driver);
  }

  public <T> T createMessage(Class<T> resultPage, String summary, String details) {
    this.summary.sendKeys(summary);
    this.text.sendKeys(details);
    this.submit.click();
    return PageFactory.initElements(driver, resultPage);
  }

  public static CreateMessagePage to(WebDriver driver) {
    driver.get("http://localhost:9990/mail/messages/form");
    return PageFactory.initElements(driver, CreateMessagePage.class);
  }
}

1	`CreateMessagePage` extends the `AbstractPage`. We do not go over the details of `AbstractPage`, but, in summary, it contains common functionality for all of our pages. For example, if our application has a navigational bar, global error messages, and other features, we can place this logic in a shared location.
2	We have a member variable for each of the parts of the HTML page in which we are interested. These are of type `WebElement`. WebDriver’s `PageFactory` lets us remove a lot of code from the HtmlUnit version of `CreateMessagePage` by automatically resolving each `WebElement`. The `PageFactory#initElements(WebDriver,Class<T>)` method automatically resolves each `WebElement` by using the field name and looking it up by the `id` or `name` of the element within the HTML page.
3	We can use the `@FindBy` annotation to override the default lookup behavior. Our example shows how to use the `@FindBy` annotation to look up our submit button with a `css` selector (`input[type=submit]`).

Finally, we can verify that a new message was created successfully. The following assertions use the AssertJ assertion library:

assertThat(viewMessagePage.getMessage()).isEqualTo(expectedMessage);
assertThat(viewMessagePage.getSuccess()).isEqualTo("Successfully created a new message");

We can see that our ViewMessagePage lets us interact with our custom domain model. For example, it exposes a method that returns a Message object:

public Message getMessage() throws ParseException {
	Message message = new Message();
	message.setId(getId());
	message.setCreated(getCreated());
	message.setSummary(getSummary());
	message.setText(getText());
	return message;
}

We can then use the rich domain objects in our assertions.

Lastly, we must not forget to close the WebDriver instance when the test is complete, as follows:

Java

@AfterEach
void destroy() {
	if (driver != null) {
		driver.close();
	}
}

For additional information on using WebDriver, see the Selenium WebDriver documentation.

Advanced `MockMvcHtmlUnitDriverBuilder`

In the examples so far, we have used MockMvcHtmlUnitDriverBuilder in the simplest way possible, by building a WebDriver based on the WebApplicationContext loaded for us by the Infra TestContext Framework. This approach is repeated here, as follows:

Java

WebDriver driver;

@BeforeEach
void setup(WebApplicationContext context) {
  driver = MockMvcHtmlUnitDriverBuilder
      .webAppContextSetup(context)
      .build();
}

We can also specify additional configuration options, as follows:

WebDriver driver;

@BeforeEach
void setup() {
  driver = MockMvcHtmlUnitDriverBuilder
      // demonstrates applying a MockMvcConfigurer (Infra Security)
      .webAppContextSetup(context, springSecurity())
      // for illustration only - defaults to ""
      .contextPath("")
      // By default MockMvc is used for localhost only;
      // the following will use MockMvc for example.com and example.org as well
      .useMockMvcForHosts("example.com","example.org")
      .build();
}

As an alternative, we can perform the exact same setup by configuring the MockMvc instance separately and supplying it to the MockMvcHtmlUnitDriverBuilder, as follows:

MockMvc mockMvc = MockMvcBuilders
    .webAppContextSetup(context)
    .apply(springSecurity())
    .build();

driver = MockMvcHtmlUnitDriverBuilder
    .mockMvcSetup(mockMvc)
    // for illustration only - defaults to ""
    .contextPath("")
    // By default MockMvc is used for localhost only;
    // the following will use MockMvc for example.com and example.org as well
    .useMockMvcForHosts("example.com","example.org")
    .build();

This is more verbose, but, by building the WebDriver with a MockMvc instance, we have the full power of MockMvc at our fingertips.

For additional information on creating a MockMvc instance, see Setup Choices.

MockMvc and WebDriver

Why WebDriver and MockMvc?

MockMvc and WebDriver Setup

MockMvc and WebDriver Usage

Advanced MockMvcHtmlUnitDriverBuilder

Advanced `MockMvcHtmlUnitDriverBuilder`