docs/html/training/testing/ui-testing/espresso-testing.jd

page.title=Testing UI for a Single App
page.tags=testing,espresso
trainingnavtop=true

@jd:body

<!-- This is the training bar -->
<div id="tb-wrapper">
<div id="tb">
  <h2>Dependencies and Prerequisites</h2>

        <ul>
          <li>Android 2.2 (API level 8) or higher
          </li>

          <li>
            <a href="{@docRoot}tools/testing-support-library/index.html">Android Testing Support
            Library</a>
          </li>
        </ul>

        <h2>
          This lesson teaches you to
        </h2>

        <ol>
          <li>
            <a href="#setup">Set Up Espresso</a>
          </li>

          <li>
            <a href="#build">Create an Espresso Test Class</a>
          </li>

          <li>
            <a href="#run">Run Espresso Tests on a Device or Emulator</a>
          </li>
        </ol>

        <h2>
          You should also read
        </h2>

        <ul>
           <li><a href="{@docRoot}reference/android/support/test/package-summary.html">
              Espresso API Reference</a></li>
        </ul>

        <h2>
          Try it out
        </h2>

        <ul>
          <li>
            <a href="https://github.com/googlesamples/android-testing"
            class="external-link">Espresso Code Samples</a>
          </li>
          <li><a href="https://www.code-labs.io/codelabs/android-testing/index.html?index=..%2F..%2Findex#0"
            class="external-link">Android Testing Codelab</a></li>
        </ul>
      </div>
    </div>

    <p>
      Testing user interactions
      within a single app helps to ensure that users do not
      encounter unexpected results or have a poor experience when interacting with your app.
      You should get into the habit of creating user interface (UI) tests if you need to verify
      that the UI of your app is functioning correctly.
    </p>

    <p>
      The Espresso testing framework, provided by the
      <a href="{@docRoot}tools/testing-support-library/index.html">Android Testing Support Library</a>,
      provides APIs for writing UI tests to simulate user interactions within a
      single target app. Espresso tests can run on devices running Android 2.2 (API level 8) and
      higher. A key benefit of using Espresso is that it provides automatic synchronization of test
      actions with the UI of the app you are testing. Espresso detects when the main thread is idle,
      so it is able to run your test commands at the appropriate time, improving the reliability of
      your tests. This capability also relieves you from having to adding any timing workarounds,
      such as a sleep period, in your test code.
    </p>

    <p>
      The Espresso testing framework is an instrumentation-based API and works
      with the
      <a href="{@docRoot}reference/android/support/test/runner/AndroidJUnitRunner.html">{@code
      AndroidJUnitRunner}</a> test runner.
    </p>

    <h2 id="setup">
      Set Up Espresso
    </h2>

<p>Before building your UI test with Espresso, make sure to configure your test source code
location and project dependencies, as described in
<a href="{@docRoot}training/testing/start/index.html#config-instrumented-tests">
Getting Started with Testing</a>.</p>

<p>In the {@code build.gradle} file of your Android app module, you must set a dependency
  reference to the Espresso library:</p>

<pre>
dependencies {
    ...
    androidTestCompile 'com.android.support.test.espresso:espresso-core:2.2.1'
}
</pre>

<p>Turn off animations on your test device &mdash; leaving system animations turned on in the test
device might cause unexpected results or may lead your test to fail. Turn off animations from
<em>Settings</em> by opening <em>Developing Options</em> and turning all the following options off:
</p>
        <ul>
          <li>
            <strong>Window animation scale</strong>
          </li>

          <li>
            <strong>Transition animation scale</strong>
          </li>

          <li>
            <strong>Animator duration scale</strong>
          </li>
        </ul>
      </li>
    </ul>
<p>If you want to set up your project to use Espresso features other than what the core API
  provides, see this
  <a href="https://google.github.io/android-testing-support-library/docs/espresso/index.html"
  class="external-link">resource</a>.</p>

    <h2 id="build">
      Create an Espresso Test Class
    </h2>

    <p>
      To create an Espresso test, create a Java class that follows this programming model:
    </p>

    <ol>
      <li>Find the UI component you want to test in an {@link android.app.Activity} (for example, a
      sign-in button in the app) by calling the
      <a href="{@docRoot}reference/android/support/test/espresso/Espresso.html#onView(org.hamcrest.Matcher<android.view.View>)">
        {@code onView()}</a> method, or the
      <a href="{@docRoot}reference/android/support/test/espresso/Espresso.html#onData(org.hamcrest.Matcher<java.lang.Object>)">
      {@code onData()}</a> method for {@link android.widget.AdapterView} controls.
      </li>

      <li>Simulate a specific user interaction to perform on that UI component, by calling the
      <a href="{@docRoot}reference/android/support/test/espresso/ViewInteraction.html#perform(android.support.test.espresso.ViewAction...)">{@code ViewInteraction.perform()}</a>
      or
      <a href="{@docRoot}reference/android/support/test/espresso/DataInteraction.html#perform(android.support.test.espresso.ViewAction...)">{@code DataInteraction.perform()}</a>
      method and passing in the user action (for example, click on the sign-in button). To sequence
      multiple actions on the same UI component, chain them using a comma-separated list in your
      method argument.
      </li>

      <li>Repeat the steps above as necessary, to simulate a user flow across multiple
      activities in the target app.
      </li>

      <li>Use the
    <a href="{@docRoot}reference/android/support/test/espresso/assertion/ViewAssertions.html">{@code ViewAssertions}</a>
        methods to check that the UI reflects the expected
      state or behavior, after these user interactions are performed.
      </li>
    </ol>

    <p>
      These steps are covered in more detail in the sections below.
    </p>

    <p>
      The following code snippet shows how your test class might invoke this basic workflow:
    </p>

<pre>
onView(withId(R.id.my_view))            // withId(R.id.my_view) is a ViewMatcher
        .perform(click())               // click() is a ViewAction
        .check(matches(isDisplayed())); // matches(isDisplayed()) is a ViewAssertion
</pre>
<h3 id="espresso-atr">Using Espresso with ActivityTestRule</h3>
<p>
The following section describes how to create a new Espresso test in the JUnit 4 style and use
<a href="{@docRoot}reference/android/support/test/rule/ActivityTestRule.html">
{@code ActivityTestRule}</a> to reduce the amount of boilerplate code you need to write. By using
<a href="{@docRoot}reference/android/support/test/rule/ActivityTestRule.html">
{@code ActivityTestRule}</a>, the testing framework launches the activity under test
before each test method annotated with {@code &#64;Test} and before any method annotated with
{@code &#64;Before}. The framework handles shutting down the activity after the test finishes
and all methods annotated with {@code &#64;After} are run.</p>

<pre>
package com.example.android.testing.espresso.BasicSample;

import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;

import android.support.test.rule.ActivityTestRule;
import android.support.test.runner.AndroidJUnit4;
...

&#64;RunWith(AndroidJUnit4.class)
&#64;LargeTest
public class ChangeTextBehaviorTest {

    private String mStringToBetyped;

    &#64;Rule
    public ActivityTestRule&lt;MainActivity&gt; mActivityRule = new ActivityTestRule&lt;&gt;(
            MainActivity.class);

    &#64;Before
    public void initValidString() {
        // Specify a valid string.
        mStringToBetyped = "Espresso";
    }

    &#64;Test
    public void changeText_sameActivity() {
        // Type text and then press the button.
        onView(withId(R.id.editTextUserInput))
                .perform(typeText(mStringToBetyped), closeSoftKeyboard());
        onView(withId(R.id.changeTextBt)).perform(click());

        // Check that the text was changed.
        onView(withId(R.id.textToBeChanged))
                .check(matches(withText(mStringToBetyped)));
    }
}
</pre>

    <h3 id="espresso-aitc2">
      Using Espresso with ActivityInstrumentationTestCase2
    </h3>
<p>The following section describes how to migrate to Espresso if you have existing test classes
subclassed from {@link android.test.ActivityInstrumentationTestCase2} and you don't want to rewrite
them to use JUnit4.</p>
<p class="note"><strong>Note:</strong> For new UI tests, we strongly recommend that you write your
test in the JUnit 4 style and use the
<a href="{@docRoot}reference/android/support/test/rule/ActivityTestRule.html">
{@code ActivityTestRule}</a> class, instead of
{@link android.test.ActivityInstrumentationTestCase2}.</p>
    <p>
      If you are subclassing {@link android.test.ActivityInstrumentationTestCase2}
      to create your Espresso test class, you must inject an
      {@link android.app.Instrumentation} instance into your test class. This step is required in
      order for your Espresso test to run with the
      <a href="{@docRoot}reference/android/support/test/runner/AndroidJUnitRunner.html">{@code AndroidJUnitRunner}</a>
      test runner.
    </p>

    <p>
      To do this, call the
      {@link android.test.InstrumentationTestCase#injectInstrumentation(android.app.Instrumentation) injectInstrumentation()}
      method and pass in the result of
      <a href="{@docRoot}reference/android/support/test/InstrumentationRegistry.html#getInstrumentation()">
      {@code InstrumentationRegistry.getInstrumentation()}</a>, as shown in the following code
      example:
    </p>

<pre>
import android.support.test.InstrumentationRegistry;

public class MyEspressoTest
        extends ActivityInstrumentationTestCase2&lt;MyActivity&gt; {

    private MyActivity mActivity;

    public MyEspressoTest() {
        super(MyActivity.class);
    }

    &#64;Before
    public void setUp() throws Exception {
        super.setUp();
        injectInstrumentation(InstrumentationRegistry.getInstrumentation());
        mActivity = getActivity();
    }

   ...
}
</pre>

<p class="note"><strong>Note:</strong> Previously, {@link android.test.InstrumentationTestRunner}
would inject the {@link android.app.Instrumentation} instance, but this test runner is being
deprecated.</p>

    <h3 id="accessing-ui-components">
      Accessing UI Components
    </h3>

    <p>
      Before Espresso can interact with the app under test, you must first specify the UI component
      or <em>view</em>. Espresso supports the use of
<a href="http://hamcrest.org/" class="external-link">Hamcrest matchers</a>
      for specifying views and adapters in your app.
    </p>

    <p>
      To find the view, call the <a href="{@docRoot}reference/android/support/test/espresso/Espresso.html#onView(org.hamcrest.Matcher<android.view.View>)">
      {@code onView()}</a>
      method and pass in a view matcher that specifies the view that you are targeting. This is
      described in more detail in <a href="#specifying-view-matcher">Specifying a View Matcher</a>.
      The <a href="{@docRoot}reference/android/support/test/espresso/Espresso.html#onView(org.hamcrest.Matcher<android.view.View>)">
      {@code onView()}</a> method returns a
      <a href="{@docRoot}reference/android/support/test/espresso/ViewInteraction.html">
      {@code ViewInteraction}</a>
      object that allows your test to interact with the view.
      However, calling  the <a href="{@docRoot}reference/android/support/test/espresso/Espresso.html#onView(org.hamcrest.Matcher<android.view.View>)">
      {@code onView()}</a> method may not work if you want to locate a view in
      an {@link android.widget.AdapterView} layout. In this case, follow the instructions in
      <a href="#locating-adpeterview-view">Locating a view in an AdapterView</a> instead.
    </p>

    <p class="note">
      <strong>Note</strong>: The <a href="{@docRoot}reference/android/support/test/espresso/Espresso.html#onView(org.hamcrest.Matcher<android.view.View>)">
      {@code onView()}</a> method does not check if the view you specified is
      valid. Instead, Espresso searches only the current view hierarchy, using the matcher provided.
      If no match is found, the method throws a
      <a href="{@docRoot}reference/android/support/test/espresso/NoMatchingViewException.html">
      {@code NoMatchingViewException}</a>.
    </p>

    <p>
      The following code snippet shows how you might write a test that accesses an
      {@link android.widget.EditText} field, enters a string of text, closes the virtual keyboard,
      and then performs a button click.
    </p>

<pre>
public void testChangeText_sameActivity() {
    // Type text and then press the button.
    onView(withId(R.id.editTextUserInput))
            .perform(typeText(STRING_TO_BE_TYPED), closeSoftKeyboard());
    onView(withId(R.id.changeTextButton)).perform(click());

    // Check that the text was changed.
    ...
}
</pre>

    <h4 id="specifying-view-matcher">
      Specifying a View Matcher
    </h4>

    <p>
      You can specify a view matcher by using these approaches:
    </p>

    <ul>
      <li>Calling methods in the
        <a href="{@docRoot}reference/android/support/test/espresso/matcher/ViewMatchers.html">
        {@code ViewMatchers}</a> class. For example, to find a view by looking for a text string it
        displays, you can call a method like this:
        <pre>
onView(withText("Sign-in"));
</pre>

<p>Similarly you can call
<a href="{@docRoot}reference/android/support/test/espresso/matcher/ViewMatchers.html#withId(int)">
{@code withId()}</a> and providing the resource ID ({@code R.id}) of the view, as shown in the
following example:</p>

<pre>
onView(withId(R.id.button_signin));
</pre>

    <p>
      Android resource IDs are not guaranteed to be unique. If your test attempts to match to a
      resource ID used by more than one view, Espresso throws an
<a href="{@docRoot}reference/android/support/test/espresso/AmbiguousViewMatcherException.html">
  {@code AmbiguousViewMatcherException}</a>.
    </p>
      </li>
      <li>Using the Hamcrest
      <a href="http://hamcrest.org/JavaHamcrest/javadoc/1.3/org/hamcrest/Matchers.html"
         class="external-link">{@code Matchers}</a> class. You can use the
      {@code allOf()} methods to combine multiple matchers, such as
      {@code containsString()} and {@code instanceOf()}. This approach allows you to
      filter the match results more narrowly, as shown in the following example:
<pre>
onView(allOf(withId(R.id.button_signin), withText("Sign-in")));
</pre>
<p>You can use the {@code not} keyword to filter for views that don't correspond to the matcher, as
shown in the following example:</p>
<pre>
onView(allOf(withId(R.id.button_signin), not(withText("Sign-out"))));
</pre>
<p>To use these methods in your test, import the {@code org.hamcrest.Matchers} package. To
learn more about Hamcrest matching, see the
<a href="http://hamcrest.org/" class="external-link">Hamcrest site</a>.
</p>
      </li>
    </ul>

    <p>
      To improve the performance of your Espresso tests, specify the minimum matching information
      needed to find your target view. For example, if a view is uniquely identifiable by its
      descriptive text, you do not need to specify that it is also assignable from the
      {@link android.widget.TextView} instance.
    </p>

    <h4 id="#locating-adpeterview-view">
      Locating a view in an AdapterView
    </h4>

    <p>
      In an {@link android.widget.AdapterView} widget, the view is dynamically populated with child
      views at runtime. If the target view you want to test is inside an
      {@link android.widget.AdapterView}
      (such as a {@link android.widget.ListView}, {@link android.widget.GridView}, or
      {@link android.widget.Spinner}), the
<a href="{@docRoot}reference/android/support/test/espresso/Espresso.html#onView(org.hamcrest.Matcher<android.view.View>)">
  {@code onView()}</a> method might not work because only a
      subset of the views may be loaded in the current view hierarchy.
    </p>

    <p>
      Instead, call the <a href="{@docRoot}reference/android/support/test/espresso/Espresso.html#onData(org.hamcrest.Matcher<java.lang.Object>)">{@code onData()}</a>
      method to obtain a
      <a href="{@docRoot}reference/android/support/test/espresso/DataInteraction.html">
      {@code DataInteraction}</a>
      object to access the target view element. Espresso handles loading the target view element
      into the current view hierarchy. Espresso also takes care of scrolling to the target element,
      and putting the element into focus.
    </p>

    <p class="note">
      <strong>Note</strong>: The
  <a href="{@docRoot}reference/android/support/test/espresso/Espresso.html#onData(org.hamcrest.Matcher<java.lang.Object>)">{@code onData()}</a>
      method does not check if if the item you specified corresponds with a view. Espresso searches
      only the current view hierarchy. If no match is found, the method throws a
      <a href="{@docRoot}reference/android/support/test/espresso/NoMatchingViewException.html">
        {@code NoMatchingViewException}</a>.
    </p>

    <p>
      The following code snippet shows how you can use the
      <a href="{@docRoot}reference/android/support/test/espresso/Espresso.html#onData(org.hamcrest.Matcher<java.lang.Object>)">{@code onData()}</a>
      method together
      with Hamcrest matching to search for a specific row in a list that contains a given string.
      In this example, the {@code LongListActivity} class contains a list of strings exposed
      through a {@link android.widget.SimpleAdapter}.
    </p>

<pre>
onData(allOf(is(instanceOf(Map.class)),
        hasEntry(equalTo(LongListActivity.ROW_TEXT), is(str))));
</pre>

    <h3 id="perform-actions">
      Performing Actions
    </h3>

    <p>
      Call the <a href="{@docRoot}reference/android/support/test/espresso/ViewInteraction.html#perform(android.support.test.espresso.ViewAction...)">{@code ViewInteraction.perform()}</a>
      or
      <a href="{@docRoot}reference/android/support/test/espresso/DataInteraction.html#perform(android.support.test.espresso.ViewAction...)">{@code DataInteraction.perform()}</a>
      methods to
      simulate user interactions on the UI component. You must pass in one or more
      <a href="{@docRoot}reference/android/support/test/espresso/ViewAction.html">{@code ViewAction}</a>
      objects as arguments. Espresso fires each action in sequence according to
      the given order, and executes them in the main thread.
    </p>

    <p>
      The
      <a href="{@docRoot}reference/android/support/test/espresso/action/ViewActions.html">{@code ViewActions}</a>
      class provides a list of helper methods for specifying common actions.
      You can use these methods as convenient shortcuts instead of creating and configuring
      individual <a href="{@docRoot}reference/android/support/test/espresso/ViewAction.html">{@code ViewAction}</a>
      objects. You can specify such actions as:
    </p>

    <ul>
      <li>
       <a href="{@docRoot}reference/android/support/test/espresso/action/ViewActions.html#click()">{@code ViewActions.click()}</a>:
       Clicks on the view.
      </li>

      <li>
       <a href="{@docRoot}reference/android/support/test/espresso/action/ViewActions.html#typeText(java.lang.String)">{@code ViewActions.typeText()}</a>:
       Clicks on a view and enters a specified string.
      </li>

      <li>
       <a href="{@docRoot}reference/android/support/test/espresso/action/ViewActions.html#scrollTo()">{@code ViewActions.scrollTo()}</a>:
       Scrolls to the view. The
        target view must be subclassed from {@link android.widget.ScrollView}
        and the value of its
        <a href="http://developer.android.com/reference/android/view/View.html#attr_android:visibility">{@code android:visibility}</a>
        property must be {@link android.view.View#VISIBLE}. For views that extend
        {@link android.widget.AdapterView} (for example,
        {@link android.widget.ListView}),
        the
        <a href="{@docRoot}reference/android/support/test/espresso/Espresso.html#onData(org.hamcrest.Matcher<java.lang.Object>)">{@code onData()}</a>
        method takes care of scrolling for you.
      </li>

      <li>
       <a href="{@docRoot}reference/android/support/test/espresso/action/ViewActions.html#pressKey(int)">{@code ViewActions.pressKey()}</a>:
       Performs a key press using a specified keycode.
      </li>

      <li>
      <a href="{@docRoot}reference/android/support/test/espresso/action/ViewActions.html#clearText()">{@code ViewActions.clearText()}</a>:
      Clears the text in the target view.
      </li>
    </ul>

    <p>
      If the target view is inside a {@link android.widget.ScrollView}, perform the
      <a href="{@docRoot}reference/android/support/test/espresso/action/ViewActions.html#scrollTo()">{@code ViewActions.scrollTo()}</a>
      action first to display the view in the screen before other proceeding
      with other actions. The
      <a href="{@docRoot}reference/android/support/test/espresso/action/ViewActions.html#scrollTo()">{@code ViewActions.scrollTo()}</a>
      action will have no effect if the view is already displayed.
    </p>

    <h3 id="verify-results">
      Verifying Results
    </h3>

    <p>
      Call the
      <a href="{@docRoot}reference/android/support/test/espresso/ViewInteraction.html#check(android.support.test.espresso.ViewAssertion)">{@code ViewInteraction.check()}</a>
      or
      <a href="{@docRoot}reference/android/support/test/espresso/DataInteraction.html#check(android.support.test.espresso.ViewAssertion)">{@code DataInteraction.check()}</a>
      method to assert
      that the view in the UI matches some expected state. You must pass in a
      <a href="{@docRoot}reference/android/support/test/espresso/ViewAssertion.html">
      {@code ViewAssertion}</a> object as the argument. If the assertion fails, Espresso throws
      an {@link junit.framework.AssertionFailedError}.
    </p>

    <p>
      The
  <a href="{@docRoot}reference/android/support/test/espresso/assertion/ViewAssertions.html">{@code ViewAssertions}</a>
      class provides a list of helper methods for specifying common
      assertions. The assertions you can use include:
    </p>

    <ul>
      <li>
        <a href="{@docRoot}reference/android/support/test/espresso/assertion/ViewAssertions.html#doesNotExist()">{@code doesNotExist}</a>:
Asserts that there is no view matching the specified criteria in the current view hierarchy.
      </li>

      <li>
        <a href="{@docRoot}reference/android/support/test/espresso/assertion/ViewAssertions.html#matches(org.hamcrest.Matcher&lt;? super android.view.View&gt;)">{@code matches}</a>:
        Asserts that the specified view exists in the current view hierarchy
        and its state matches some given Hamcrest matcher.
      </li>

      <li>
       <a href="{@docRoot}reference/android/support/test/espresso/assertion/ViewAssertions.html#selectedDescendantsMatch(org.hamcrest.Matcher&lt;android.view.View&gt;, org.hamcrest.Matcher&lt;android.view.View&gt;)">{@code selectedDescendentsMatch}</a>
       : Asserts that the specified children views for a
        parent view exist, and their state matches some given Hamcrest matcher.
      </li>
    </ul>

    <p>
      The following code snippet shows how you might check that the text displayed in the UI has
      the same value as the text previously entered in the
      {@link android.widget.EditText} field.
    </p>
<pre>
public void testChangeText_sameActivity() {
    // Type text and then press the button.
    ...

    // Check that the text was changed.
    onView(withId(R.id.textToBeChanged))
            .check(matches(withText(STRING_TO_BE_TYPED)));
}
</pre>

<h2 id="run">Run Espresso Tests on a Device or Emulator</h2>
<p>
You can run Espresso tests from <a href="{@docRoot}studio/index.html">Android Studio</a> or
from the command-line. Make sure to specify
<a href="{@docRoot}reference/android/support/test/runner/AndroidJUnitRunner.html">
  {@code AndroidJUnitRunner}</a> as the default instrumentation runner in your project.
</p>
<p>
To run your Espresso test, follow the steps for running instrumented tests
described in <a href="{@docRoot}training/testing/start/index.html#run-instrumented-tests">
Getting Started with Testing</a>.</p>