How to android unit test and mock a static method

Question

Hi I really hope you can help me, I feel like I've been pulling my hair out for days.

I'm trying to write unit tests for a method A. Method A calls a static method B. I want to mock static method B.

I know this has been asked before, but I feel Android has matured since then, and there must be a way to do such a simple task without re-writing the methods I want to test.

Here is an example, first the method I want to test:

public String getUserName(Context context, HelperUtils helper) {
    if(helper == null){
        helper = new HelperUtils();
    }
    int currentUserId = helper.fetchUsernameFromInternet(context);

    if (currentUserId == 1) {
        return "Bob";
    } else {
        return "Unknown";
    }
}

Next the static method I want to mock:

public class HelperUtils {
    public static int fetchUsernameFromInternet(Context context) {
        int userid = 0;

        Log.i("HelperUtils ", "hello");

        return userid;
    }
}

In other languages this is so easy but I just can't make it work in Android. I've tried Mockito, but it appears static methods aren't supported

HelperUtils helper = Mockito.mock(HelperUtils.class);
Mockito.when(helper.fetchUsernameFromInternet(getContext())).thenReturn(1);

This errors

org.mockito.exceptions.misusing.MissingMethodInvocationException

I've tried Powermock but I'm not completely sure this is supported by Android. I managed to get powermock running using androidCompile in my gradle file but I get this error:

Error:Execution failed for task ':app:dexDebugAndroidTest'. com.android.ide.common.process.ProcessException:

Not to mention PowerMockito.mockStatic(HelperUtils.class); Doesn't return anything, so I don't know what to pass into my getUsername method!

Any help would be so very much appreciated.

Answer 1

Static methods aren't related to any object - your helper.fetchUsernameFromInternet(...) is the same (but a bit confusing) as HelperUtils.fetchUsernameFromInternet(...) - you should even get a compiler warning due to this helper.fetchUsernameFromInternet .

What's more, instead of Mockito.mock to mock static methods you have to use: @RunWith(...) , @PrepareForTest(...) and then PowerMockito.mockStatic(...) - complete example is here: PowerMockito mock single static method and return object

In other words - mocking static methods (and also constructors) is a bit tricky. Better solution is:

• if you can change HelperUtils , make that method non-static and now you can mock HelperUtils with the usual Mockito.mock

• if you can't change HelperUtils , create a wrapper class which delegates to the original HelperUtils , but doesn't have static methods, and then also use usual Mockito.mock (this idea is sometimes called "don't mock types you don't own")

Answer 2

I did this way using PowerMockito .

I am using AppUtils.class , it contains multiple static methods and functions.

Static function:

public static boolean isValidEmail(CharSequence target) {
    return target != null && EMAIL_PATTERN.matcher(target).matches();
}

Test case:

@RunWith(PowerMockRunner.class)
@PrepareForTest({AppUtils.class})
public class AppUtilsTest {

    @Before
    public void setUp() throws Exception {
        MockitoAnnotations.initMocks(this);
        PowerMockito.mockStatic(AppUtils.class);

        PowerMockito.when(AppUtils.isValidEmail(anyString())).thenCallRealMethod();
    }

    @Test
    public void testValidEmail() {
        assertTrue(AppUtils.isValidEmail("name@email.com"));
    }

    @Test
    public void testInvalidEmail1() {
        assertFalse(AppUtils.isValidEmail("name@email..com"));
    }

    @Test
    public void testInvalidEmail2() {
        assertFalse(AppUtils.isValidEmail("@email.com"));
    }
}

Edit 1:

Add following imports:

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;

Hope this would help you.

Answer 3

You can use mockito latest version ie 3.4.+ which allows static mocking

https://javadoc.io/doc/org.mockito/mockito-core/latest/org/mockito/Mockito.html#48

Answer 4

Here are some solutions:

• Modify your static method as a non-static method or wrap your static method with a non-static method, and then directly use Mockito to mock the non-static method in the Android Test.
• If you don't want to change any original code, you can try to use a dexmaker-mockito-inline-extended to mock static methods and final methods in the Android Test. I successfully mocked the static methods with it. Check this solution .
• Use a Robolectric in the Unit test and then use PowerMock to mock the static methods in the Unit Test.