How to mock a SharedPreferences using Mockito

Question

I have just read about Unit Instrumented Testing in Android and I wonder how I can mock a SharedPreferences without any SharedPreferencesHelper class on it like here

Answer 1

The following example shows how you might create a unit test that uses a mock Context object such as shared preference.

@RunWith(MockitoJUnitRunner.class)
public class MProfileTest {

   @Mock
   Context mockContext;
   @Mock
   SharedPreferences mockPrefs;
   @Mock
   SharedPreferences.Editor mockEditor;

   @Before
   public void before() throws Exception {

      Mockito.when(mockContext.getSharedPreferences(anyString(), anyInt())).thenReturn(mockPrefs);
      Mockito.when(mockContext.getSharedPreferences(anyString(), anyInt()).edit()).thenReturn(mockEditor);

      Mockito.when(mockPrefs.getString("YOUR_KEY", null)).thenReturn("YOUR_VALUE");
   }

   @Test
   public void anyTest() {
      // Any shared preference you can call
      // Assert.assertTrue();
      String val = _mockPrefs.getString("YOUR_KEY", null); // It returns YOUR_VALUE
   }
}

If you face any issues on importing mock framework just make sure you have added the depencencies in your app/build.gradle file.

https://developer.android.com/training/testing/unit-testing/local-unit-tests#setup

---

If you want to use real shared prefrence as your device by storing all the data in memory, follow the below code.

Get the MockSharedPreference.java file from this Gist https://gist.github.com/aslamanver/f74a2b3d450fda251d47a0d38b44edb7

@Mock
Context mockContext;

MockSharedPreference mockPrefs;
MockSharedPreference.Editor mockPrefsEditor;

@Before
public void before() {

    mockPrefs = new MockSharedPreference();
    mockPrefsEditor = mockPrefs.edit();

    Mockito.when(mockContext.getSharedPreferences(anyString(), anyInt())).thenReturn(mockPrefs);
}