Monday, January 6, 2014

Discovering Espresso for Android: matching and asserting view with text.

After more than a month of using great test tool from Google - Espresso for Android, I'd like to share with you some of my experience. I assume that you've already added espresso jar into your project, spent some time playing with Espresso samples and have basic understanding how this tool works.

In this post I'll show how to match particular view with text or assert that it contains (or not) specified Strings. Before we start, you have to take a look at Hamcrest matchers - Hamcrest tutorial and API Reference Documentation, which are used together with Espresso's ViewAssertions and ViewMatchers and included into Espresso standalone library. Pay more attention to Matcher<java.lang.String> matchers.

So, here we go. For simplicity following String "XXYYZZ" will be used as a expected text pattern.
Espresso ViewMatchers class implements two String matcher methods withText() and withContentDescription() which will match a view which text is equal to specified expectedText or specified expectedContentDescriptionText parameter passed into it.
onView(withText("XXYYZZ")).perform(click());
onView(withContentDescription("XXYYZZ")).perform(click()); 

 

Using Hamcrest String matchers we can create more flexible matcher combinations:

 - matching a view which text starts with "XXYY" pattern:
onView(withText(startsWith("XXYY"))).perform(click());
 - matching a view which text ends with "YYZZ" pattern:
onView(withText(endsWith("YYZZ"))).perform(click());
 - assert that text of a particular view with specified R.id has content description which contains "YYZZ" string anywhere:
onView(withId(R.id.viewId)).check(matches(withContentDescription(containsString("YYZZ"))));
 - matching a view which text is equal to the specified string, ignoring case:
onView(withText(equalToIgnoringCase("xxYY"))).perform(click());
 - matching a view which text is equal to the specified text when whitespace differences are (mostly) ignored:
onView(withText(equalToIgnoringWhiteSpace("XX YY ZZ"))).perform(click());
 - assert that text of a particular view with specified R.id does not contain "YYZZ" string:
onView(withId(R.id.viewId)).check(matches(withText(not(containsString("YYZZ")))));

 

 Adding allOf() or anyOf() Hamcrest Core matchers gives us even more power:

 - assert that text of a particular view with specified R.id doesn't start with "ZZ" string and contains "YYZZ" string anywhere:
onView(withId(R.id.viewId))
    .check(matches(allOf(withText(not(startsWith("ZZ"))), withText(containsString("YYZZ")))));
- assert that text of a particular view with specified R.id ends with "ZZ" string or contains "YYZZ" string anywhere:
onView(withId(R.id.viewId))
    .check(matches(anyOf(withText(endsWith("ZZ")), withText(containsString("YYZZ")))));
The last note - to use all of mentioned above ViewAssertions, ViewMatchers and Hamcrest matchers just add below imports:
import static com.google.android.apps.common.testing.ui.espresso.Espresso.onView;
import static com.google.android.apps.common.testing.ui.espresso.assertion.ViewAssertions.matches;
import static com.google.android.apps.common.testing.ui.espresso.matcher.ViewMatchers.withId;
import static com.google.android.apps.common.testing.ui.espresso.matcher.ViewMatchers.withText;
import static com.google.android.apps.common.testing.ui.espresso.matcher.ViewMatchers.withContentDescription;
import static org.hamcrest.Matchers.not;
import static org.hamcrest.Matchers.allOf;
import static org.hamcrest.Matchers.anyOf;
import static org.hamcrest.Matchers.containsString;
import static org.hamcrest.Matchers.startsWith;
import static org.hamcrest.Matchers.endsWith;
import static org.hamcrest.Matchers.equalToIgnoringCase;
import static org.hamcrest.Matchers.equalToIgnoringWhiteSpace;
So, basically it. If you stuck at some point and don't have an idea how to proceed, you can ask a question in androit-test-kit Google group. You'll probably get an answer from co-author of Espresso tool - +Valera Zakharov or other experienced users.

Thanks for reading!