Mock up account in ActivityInstrumentationTestCase2

Question

In my Activity, I get accounts in onCreate():

public void MyActivity extends Activity{
   ...
   private Account[] accounts;
   @Override
   protected void onCreate(){
       accounts = AccountManager.get(this).getAccounts();  
   }
   ...
}

Now, I am unit testing MyActivity in test project:

public class MyActivityTest extends ActivityInstrumentationTestCase2<MyActivity> {
    ...
    @Override
    protected void setUp() throws Exception{
       super.setUp();
      //How to mock up the accounts in system so that some fake accounts could be used
    }
    ...
}

In my above test case, I would like to use some fake accounts, how could I mock up the accounts so that AccountManager.get(this).getAccounts(); returns those mocked accounts in my project under test?

Answer 1

Try this code:

import static org.junit.Assert.assertEquals;
import static org.mockito.Matchers.any;
import static org.powermock.api.mockito.PowerMockito.mockStatic;
import static org.powermock.api.mockito.PowerMockito.when;

import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest(AccountManager.class)
public class MyActivityTest extends ActivityInstrumentationTestCase2<MyActivity> {
{
    @Mock
    public MyActivity myActivity;

    @Mock
    AccountManager accountManager;

    @Before
    public void setUp() throws Exception{
        MockitoAnnotations.initMocks(this);
    }

    @Test
    public void mocking() {
        mockStatic(AccountManager.class);
        when(AccountManager.get(any(MyActivity.class))).thenReturn(accountManager);
        when(accountManager.getAccounts()).thenReturn(new Account[] {});
        MyActivity activity = new MyActivity();
        activity.onCreate();
        assertEquals(0, activity.getAccounts().length);
    }

    @Test
    public void withoutMocking() {
        MyActivity activity = new MyActivity();
        activity.onCreate();
        assertEquals(2, activity.getAccounts().length);
    }

}