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
-
Kotlin
HtmlTextInput summaryInput = currentPage.getHtmlElementById("summary");
summaryInput.setValueAttribute(summary);
val 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
-
Kotlin
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);
}
fun createMessage(currentPage: HtmlPage, summary:String, text:String) :HtmlPage{
setSummary(currentPage, summary);
// ...
}
fun setSummary(currentPage:HtmlPage , summary: String) {
val 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
-
Kotlin
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());
}
}
class CreateMessagePage(private val currentPage: HtmlPage) {
val summaryInput: HtmlTextInput = currentPage.getHtmlElementById("summary")
val submit: HtmlSubmitInput = currentPage.getHtmlElementById("submit")
fun <T> createMessage(summary: String, text: String): T {
setSummary(summary)
val result = submit.click()
val error = at(result)
return (if (error) CreateMessagePage(result) else ViewMessagePage(result)) as T
}
fun setSummary(summary: String) {
summaryInput.setValueAttribute(summary)
}
fun at(page: HtmlPage): Boolean {
return "Create Message" == 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 Spring MVC Test framework, make sure that your project
includes a test dependency on org.seleniumhq.selenium:selenium-htmlunit-driver
.
We can easily create a Selenium WebDriver that integrates with MockMvc by using the
MockMvcHtmlUnitDriverBuilder
as the following example shows:
-
Java
-
Kotlin
WebDriver driver;
@BeforeEach
void setup(WebApplicationContext context) {
driver = MockMvcHtmlUnitDriverBuilder
.webAppContextSetup(context)
.build();
}
lateinit var driver: WebDriver
@BeforeEach
fun setup(context: WebApplicationContext) {
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
-
Kotlin
CreateMessagePage page = CreateMessagePage.to(driver);
val page = CreateMessagePage.to(driver)
We can then fill out the form and submit it to create a message, as follows:
-
Java
-
Kotlin
ViewMessagePage viewMessagePage =
page.createMessage(ViewMessagePage.class, expectedSummary, expectedText);
val 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:
-
Java
-
Kotlin
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] ). |
class CreateMessagePage(private val driver: WebDriver) : AbstractPage(driver) { (1)
(2)
private lateinit var summary: WebElement
private lateinit var text: WebElement
@FindBy(css = "input[type=submit]") (3)
private lateinit var submit: WebElement
fun <T> createMessage(resultPage: Class<T>, summary: String, details: String): T {
this.summary.sendKeys(summary)
text.sendKeys(details)
submit.click()
return PageFactory.initElements(driver, resultPage)
}
companion object {
fun to(driver: WebDriver): CreateMessagePage {
driver.get("http://localhost:9990/mail/messages/form")
return PageFactory.initElements(driver, CreateMessagePage::class.java)
}
}
}
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:
-
Java
-
Kotlin
assertThat(viewMessagePage.getMessage()).isEqualTo(expectedMessage);
assertThat(viewMessagePage.getSuccess()).isEqualTo("Successfully created a new message");
assertThat(viewMessagePage.message).isEqualTo(expectedMessage)
assertThat(viewMessagePage.success).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:
-
Java
-
Kotlin
public Message getMessage() throws ParseException {
Message message = new Message();
message.setId(getId());
message.setCreated(getCreated());
message.setSummary(getSummary());
message.setText(getText());
return message;
}
fun getMessage() = Message(getId(), getCreated(), getSummary(), getText())
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
-
Kotlin
@AfterEach
void destroy() {
if (driver != null) {
driver.close();
}
}
@AfterEach
fun 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 Spring TestContext Framework. This approach is repeated here, as follows:
-
Java
-
Kotlin
WebDriver driver;
@BeforeEach
void setup(WebApplicationContext context) {
driver = MockMvcHtmlUnitDriverBuilder
.webAppContextSetup(context)
.build();
}
lateinit var driver: WebDriver
@BeforeEach
fun setup(context: WebApplicationContext) {
driver = MockMvcHtmlUnitDriverBuilder
.webAppContextSetup(context)
.build()
}
We can also specify additional configuration options, as follows:
-
Java
-
Kotlin
WebDriver driver;
@BeforeEach
void setup() {
driver = MockMvcHtmlUnitDriverBuilder
// demonstrates applying a MockMvcConfigurer (Spring 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();
}
lateinit var driver: WebDriver
@BeforeEach
fun setup() {
driver = MockMvcHtmlUnitDriverBuilder
// demonstrates applying a MockMvcConfigurer (Spring 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:
-
Java
-
Kotlin
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();
// Not possible in Kotlin until https://youtrack.jetbrains.com/issue/KT-22208 is fixed
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.
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