使用PowerMock / Mockito时，模拟对象为null

Question

I am trying to unit test one of my methods using PowerMock and Mockito and getting NUllPointerException for one of the objects which I have already mocked and defined behavior in my test.

This is the code I am trying to test

protected void setTabList() {

    List<ActionBar.Tab> list = TabAdapter.get().getAllEnabledTabs();
    listAdapter.setTabList(list);

    int itemCount = list.size();
    if (itemCount == 1 && list.get(0).equals(TabAdapter.KEYPAD_TAB)) {
        header.setVisibility(View.VISIBLE);
        listAdapter.hide();
    }
}

And this is the test code

@RunWith(PowerMockRunner.class)

@PrepareForTest({Log.class, TabFragment.class, TextView.class, SystemProperties.class})

public class TabFragmentTests extends TestCase {

    @Before
    public void setUp() {
        suppress(method(Log.class, "println_native"));
        suppress(everythingDeclaredIn(TextView.class));
        suppress(method(SystemProperties.class, "native_get_boolean"));
        suppress(method(SystemProperties.class, "native_get", String.class));

        tabFragment = new TabFragment();
        listAdapter = Mockito.mock(TabList.class);

    }

    @Test
    public void testSetTabList() {
        assertNotNull(tabFragment);
        assertNotNull(listAdapter);

        TabAdapter instance = TabAdapter.get();
        TabAdapter spy = spy(instance);

        List<ActionBar.Tab> list = new ArrayList<ActionBar.Tab>();
        list.add(KEYPAD_TAB);

        doAnswer(new Answer<String>() {
            @Override 
            public String answer (InvocationOnMock invocation) {
                return "set Tabs";
            }
        }).when(listAdapter).setTabList(list);

        doAnswer(new Answer<String>() {
            @Override 
            public String answer (InvocationOnMock invocation) {
                return "hide";
            }
        }).when(listAdapter).hide();


        doReturn(list).when(spy).getAllEnabledTabs();
        tabFragment.setTabList();


        verify(listAdapter, times(1)).hide();
    }

When I run the test and tabFragment.setTabList() is called, listAdapter in setTabList() throws NPE. I am trying to understand why listAdapter.setTabList(list) is not replaced by the "answer" API I have in the test.

I have also tried using Mockito.doNothing().when(listAdapter).setTabList(list) but that doesn't solve the issue.

Another observation is when I create a dummy getTestString(listAdapter) method in my TabFragment class and call it using tabFragment.getTestString(listAdapter) from my test passing mocked listAdapter as an argument, it doesn't through a NPE. Does that mean I have to explicitly pass mocked object to the method call?

Answer 1

You are overriding a method call like this:

when(listAdapter).setTabList(list);

but then you call it like this:

tabFragment.setTabList();

I don't see how that would work. setTabList(list); and setTabList(); call different methods.

Answer 2

我认为您忘记将“ TabAdapter”类添加到“ PrepareForTest”批注中：

@PrepareForTest({Log.class, TabAdapter.class, TabFragment.class, TextView.class, SystemProperties.class})