PowerMocking static does not return expected object

Question

I have a problem mocking Calendar.getInstance(). As you now this method returns a Calendar - the object I am mocking.

Right now my code looks like this:

Answer 1

It seems that you need to add the target test class in the PrepareForTest tag:
@PrepareForTest({ Calendar.class, Surveillance.class })

@RunWith(PowerMockRunner.class)
@PrepareForTest({ Calendar.class, Surveillance.class })
public class SurveillanceDatabaseTest {
    @Test
    public void testFailingDatabase() throws Exception {
        mockStatic(Calendar.class);
        Calendar calendar = new GregorianCalendar();
        calendar.add(Calendar.HOUR, 1);
        when(Calendar.getInstance()).thenReturn(calendar);
        final Surveillance surveillance = new Surveillance();
        surveillance.checkDatabase();
   }
}

Even Tom Tresansky's example above will need it if we move the Surveillance class to somewhere outside MockCalendarTest class.

Answer 2

It seems like you're doing everything right. For instance, this test below passes, proving that the Calendar returned by Calendar#getInstance() is in fact the one you set up with the static mocking.

import static org.junit.Assert.*;
import static org.powermock.api.mockito.PowerMockito.*;

import java.util.Calendar;
import java.util.GregorianCalendar;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest(Calendar.class)
public class MockCalendarTest {
    @Test
    public void testFailingDatabase() {
        mockStatic(Calendar.class);

        final Calendar testCalendar = new GregorianCalendar();
        testCalendar.add(Calendar.HOUR, 1);
        when(Calendar.getInstance()).thenReturn(testCalendar);

        final Surveillance surveillance = new Surveillance();
        final Calendar resultCalendar = surveillance.checkDatabase();

        assertTrue(testCalendar == resultCalendar);
   }

    public static class Surveillance {
      public Calendar checkDatabase() {
        return Calendar.getInstance();
      }
    }
}

Perhaps post the relevant parts of the Surveillance class so we can see how it's trying to get a new Calendar and assess why it's failing.

Answer 3

I'm not as familiar with the when(object.call()).andReturn(response); but I'm assuming it works the same way as expect.(object.call()).andReturn(response);. If that is the case, then it looks like all you are missing a replay of the class PowerMock.replay(Calendar.class) and you are trying to do a full static mock instead of a partial static mock. This should resolve your issue.

@RunWith(PowerMockRunner.class)
@PrepareForTest(Calendar.class)
public class SurveillanceDatabaseTest {
    @Test
    public void testFailingDatabase() throws Exception {

        Calendar calendar = new GregorianCalendar();
        calendar.add(Calendar.HOUR, 1);

        PowerMock.mockStaticPartial(Calendar.class, "getInstance");  //Mock Static Partial
        expect(Calendar.getInstance()).andReturn(calendar);
        PowerMock.replay(Calendar.class);  // note the replay of the Class!

        final Surveillance surveillance = new Surveillance();
        surveillance.checkDatabase();

        //Whatever tests you need to do here
   }
}