Espresso-Web is an entry point to work with Android WebView UI components. Espresso-Web reuses Atoms from the popular WebDriver API to examine and control the behavior of a WebView.
When to use Espresso-Web
Use Espresso-Web to test your hybrid apps, especially the integration of your
app’s native UI components with its WebView
UI components. You can use the Espresso-Web API in conjunction with other
Espresso APIs to fully interact with web elements inside WebView
objects.
If you need to test only the WebView
itself, and not the
interactions between the WebView
and native components in your app, consider
writing a general web test using a framework like WebDriver. If you use a web testing framework, you don’t
need to use an Android device or a Java Virtual Machine, which makes your tests
run more quickly and reliably. That being said, Espresso-Web allows you to reuse
your custom WebDriver atoms, which gives you a lot of flexibility, especially
when writing tests that you plan to run against both standalone web apps and
apps that include an Android UI.
How it works
Similarly to Espresso’s onData()
method, a WebView
interaction comprises several Atoms.
WebView
interactions use a combination of the Java programming language and a
JavaScript bridge to do their work. Because there is no chance of introducing
race conditions by exposing data from the JavaScript environment—everything
Espresso sees on the Java-based side is an isolated copy—returning data from
Web.WebInteraction
objects is fully supported, allowing you to verify all data that’s returned from
a request.
What is a WebDriver Atom?
The WebDriver framework uses Atoms to find and manipulate web elements
programmatically. Atoms are used by WebDriver to allow browser manipulation. An
Atom is conceptually similar to a
ViewAction
, a self-contained
unit that performs an action in your UI. You expose Atoms using a list of
defined methods, such as findElement()
and getElement()
, to drive the
browser from the user’s point of view. However, if you use the WebDriver
framework directly, Atoms need to be properly orchestrated, requiring logic that
is quite verbose.
Within Espresso, the classes Web
and Web.WebInteraction
wrap this boilerplate and give an Espresso-like feel to interacting with WebView
objects. So in a context of a WebView
, Atoms are used as
a substitution to traditional Espresso ViewMatchers
and ViewActions
.
The API then looks quite simple:
Kotlin
onWebView() .withElement(Atom) .perform(Atom) .check(WebAssertion)
Java
onWebView() .withElement(Atom) .perform(Atom) .check(WebAssertion);
To learn more, read Selenium’s documentation on Atoms.
Implement WebView
Follow the guidance shown in the following sections to work with
WebView
in your app's tests.
Packages
To include Espresso-Web in your project, complete the following steps:
- Open your app’s
build.gradle
file. This is usually not the top-levelbuild.gradle
file butapp/build.gradle
. Add the following line inside dependencies:
Groovy
androidTestImplementation 'androidx.test.espresso:espresso-web:3.6.1'
Kotlin
androidTestImplementation('androidx.test.espresso:espresso-web:3.6.1')
Espresso-Web is only compatible with Espresso 2.2 or higher and version 0.3 or higher of the testing library, so make sure you update those lines as well:
Groovy
androidTestImplementation 'androidx.test:runner:1.6.1' androidTestImplementation 'androidx.test:rules:1.6.1' androidTestImplementation 'androidx.test.espresso:espresso-core:3.6.1'
Kotlin
androidTestImplementation('androidx.test:runner:1.6.1') androidTestImplementation('androidx.test:rules:1.6.1') androidTestImplementation('androidx.test.espresso:espresso-core:3.6.1')
Common API usage
The onWebView()
method is the main entry point when working with WebView on Android using
Espresso. You use this method to perform Espresso-Web tests, such as the
following:
Kotlin
onWebView() .withElement(findElement(Locator.ID, "link_2")) // similar to onView(withId(...)) .perform(webClick()) // Similar to perform(click()) // Similar to check(matches(...)) .check(webMatches(getCurrentUrl(), containsString("navigation_2.html")))
Java
onWebView() .withElement(findElement(Locator.ID, "link_2")) // similar to onView(withId(...)) .perform(webClick()) // Similar to perform(click()) // Similar to check(matches(...)) .check(webMatches(getCurrentUrl(), containsString("navigation_2.html")));
In this example, Espresso-Web locates a DOM element whose ID is "link_2"
and
clicks on it. The tool then verifies that the WebView sends a GET request
containing the "navigation_2.html"
string.
JavaScript support
When executing your tests, the system performs all WebView interactions using JavaScript. Therefore, to support JavaScript evaluation, the WebView under test must have JavaScript enabled.
You can force JavaScript to be enabled by calling
forceJavascriptEnabled()
as an action in your activity under
test, as shown in the
following code snippet.
@RunWith(AndroidJUnit4::class) class MyTestSuite { @get:Rule val activityScenarioRule = activityScenarioRule<MyWebViewActivity>() @Test fun testWebViewInteraction() { onWebView().forceJavascriptEnabled() } }
Common web interactions
Common interactions with Web.WebInteraction
objects include the following:
-
withElement()
references a DOM element within the WebView.Example:
Kotlin
onWebView().withElement(findElement(Locator.ID, "teacher"))
Java
onWebView().withElement(findElement(Locator.ID, "teacher"));
-
withContextualElement()
references a scoped DOM element within the WebView, relative to another DOM element. You should callwithElement()
first to establish the referenceWeb.WebInteraction
object (DOM element).Example:
Kotlin
.withElement(findElement(Locator.ID, "teacher")) .withContextualElement(findElement(Locator.ID, "person_name"))
Java
.withElement(findElement(Locator.ID, "teacher")) .withContextualElement(findElement(Locator.ID, "person_name"));
-
check()
evaluates a condition, making sure that it resolves totrue
.Example:
Kotlin
onWebView() .withElement(findElement(Locator.ID, "teacher")) .withContextualElement(findElement(Locator.ID, "person_name")) .check(webMatches(getText(), containsString("Socrates")))
Java
onWebView() .withElement(findElement(Locator.ID, "teacher")) .withContextualElement(findElement(Locator.ID, "person_name")) .check(webMatches(getText(), containsString("Socrates")));
-
perform()
executes an action within a WebView, such as clicking on an element.Example:
Kotlin
onWebView() .withElement(findElement(Locator.ID, "teacher")) .perform(webClick())
Java
onWebView() .withElement(findElement(Locator.ID, "teacher")) .perform(webClick());
-
reset()
reverts the WebView to its initial state. This is necessary when a prior action, such as a click, introduces a navigation change that makes ElementReference and WindowReference objects inaccessible.Note: Although using
reset()
is useful when making assertions against multi-page workflows, such as form submissions, your tests should usually be limited in scope and focus on a single page.Example:
Kotlin
onWebView() .withElement(...) .perform(...) .reset()
Java
onWebView() .withElement(...) .perform(...) .reset();
Example
The following example tests whether, after entering text into a WebView and selecting a Submit button, the same text appears within a different element in the same WebView:
Kotlin
const val MACCHIATO = "Macchiato" @RunWith(AndroidJUnit4::class) class MyEspressoWebTestSuite { @Test fun typeTextInInput_clickButton_SubmitsForm() { // Create an intent that displays a web form. val webFormIntent = Intent() // ... // Lazily launch the Activity with a custom start Intent per test. ActivityScenario.launchActivity(webFormIntent) // Selects the WebView in your layout. If you have multiple WebView // objects, you can also use a matcher to select a given WebView, // onWebView(withId(R.id.web_view)). onWebView() // Find the input element by ID. .withElement(findElement(Locator.ID, "text_input")) // Clear previous input and enter new text into the input element. .perform(clearElement()) .perform(DriverAtoms.webKeys(MACCHIATO)) // Find the "Submit" button and simulate a click using JavaScript. .withElement(findElement(Locator.ID, "submitBtn")) .perform(webClick()) // Find the response element by ID, and verify that it contains the // entered text. .withElement(findElement(Locator.ID, "response")) .check(webMatches(getText(), containsString(MACCHIATO))) } }
Java
public static final String MACCHIATO = "Macchiato"; @Test public void typeTextInInput_clickButton_SubmitsForm() { // Create an intent that displays a web form. Intent webFormIntent = new Intent(); // ... // Lazily launch the Activity with a custom start Intent per test. ActivityScenario.launchActivity(webFormIntent); // Selects the WebView in your layout. If you have multiple WebView objects, // you can also use a matcher to select a given WebView, // onWebView(withId(R.id.web_view)). onWebView() // Find the input element by ID. .withElement(findElement(Locator.ID, "text_input")) // Clear previous input and enter new text into the input element. .perform(clearElement()) .perform(DriverAtoms.webKeys(MACCHIATO)) // Find the "Submit" button and simulate a click using JavaScript. .withElement(findElement(Locator.ID, "submitBtn")) .perform(webClick()) // Find the response element by ID, and verify that it contains the // entered text. .withElement(findElement(Locator.ID, "response")) .check(webMatches(getText(), containsString(MACCHIATO))); }
Additional resources
For more information about using Espresso-Web in Android tests, consult the following resources.
Samples
- WebBasicSample:
Use Espresso-Web to interact with
WebView
objects.