单元测试

**xml布局**
<TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Hello World!" />
        <EditText
            android:id="@+id/editText"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="SAY HFLLO"
            android:onClick="sayHello"/>

**MainActivity.java**

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

}

public void sayHello(View view){
    TextView textView= (TextView) findViewById(R.id.textView);
    EditText editText= (EditText) findViewById(R.id.editText);
    textView.setText("Hello,"+editText.getText().toString()+"!");
}

**环境配置**

//add for test
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

//add for test
androidTestCompile 'com.android.support.test.espresso:espresso-core:2.2.2', {
    exclude group: 'com.android.support', module: 'support-annotations'
}
**测试**

public class MainActivityTest {
    private static final String STRING_TO_BE_TYPED = "Peter";
    @Rule
    public ActivityTestRule<MainActivity> mActivityRule = new ActivityTestRule<>(MainActivity.class);

    @Test
    public void sayHello() {
        onView(withId(R.id.editText))
                .perform(typeText(STRING_TO_BE_TYPED),
                        closeSoftKeyboard());

        onView(withText("Say hello!")).perform(click());

        String expectedText = "Hello," + STRING_TO_BE_TYPED + "!";
        onView(withId(R.id.textView))
                .check(matches(withText(expectedText)));
    }