Explore the technical principles of the Java library in the AndroidX Test Library framework
AndroidX Test Library (hereinafter referred to as Test Library) is a test framework for Android applications. It provides rich tools and libraries for writing and running unit testing, functional testing and UI test.In Test Library, many Java class libraries are used to achieve different types of testing and provide some technical principles.
1. JUNIT: Junit is a Java unit test framework that is widely used in Test Library.It provides a set of annotations and assertions for writing, organizing and running unit testing.Junit uses the @Test annotation marking test method to use the front and rear operations of the @Beface and @AFTER annotation marking test method.For example, the following is a simple unit test code written in Junit:
import org.junit.Test;
import static org.junit.Assert.assertEquals;
public class SampleUnitTest {
@Test
public void addition_isCorrect() {
int result = 2 + 2;
assertEquals(4, result);
}
}
Second, Espresso: Espresso is a framework for writing UI tests, which are widely used in Test Library.It provides a set of API to simulate the UI behavior of the user's operation and verify the application.The core principle of Espresso is to achieve testing by operating UI components in the application process.For example, the following is a simple UI test code written in Espresso:
import androidx.test.espresso.Espresso;
import androidx.test.espresso.action.ViewActions;
import androidx.test.espresso.matcher.ViewMatchers;
import androidx.test.rule.ActivityTestRule;
import org.junit.Rule;
import org.junit.Test;
public class SampleUITest {
@Rule
public ActivityTestRule<MainActivity> activityRule =
new ActivityTestRule<>(MainActivity.class);
@Test
public void clickButton_opensNewActivity() {
// Click the button
Espresso.onView(ViewMatchers.withId(R.id.button)).perform(ViewActions.click());
// Verify whether the new Activity is opened
Espresso.onView(ViewMatchers.withId(R.id.new_activity))
.check(ViewAssertions.matches(ViewMatchers.isDisplayed()));
}
}
3. Robolectric: RoboLectric is a framework for writing the Android unit test, which is widely used in Test Library.It provides a code that can run Android applications on the JVM when the Android environment is running.In this way, developers can conduct fast unit tests without depending on the device or simulator.The principle of Robolectric is to achieve testing by rewriting and simulating the behavior of the Android framework class.For example, the following is a simple unit test code written in RoboLectric:
import androidx.appcompat.app.AppCompatActivity;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.robolectric.Robolectric;
import org.robolectric.RobolectricTestRunner;
import static org.junit.Assert.assertEquals;
@RunWith(RobolectricTestRunner.class)
public class SampleRobolectricTest {
@Test
public void activityCreation_shouldNotBeNull() {
AppCompatActivity activity = Robolectric.setupActivity(MainActivity.class);
assertNotNull(activity);
}
}
In summary, the Java library in the Androidx Test Library framework uses different technical principles to implement unit testing, functional testing and UI test.Junit is used to write and run unit testing, Espresso is used to write and run UI tests, and Robolectric is used to run Android application code on JVM for unit testing.The use of these class libraries enables developers to test more conveniently and improve the quality and stability of applications.
