How to mock a SharedPreferences using Mockito

So, because SharedPreferences comes from your context, it's easy:

final SharedPreferences sharedPrefs = Mockito.mock(SharedPreferences.class);
final Context context = Mockito.mock(Context.class);
Mockito.when(context.getSharedPreferences(anyString(), anyInt())).thenReturn(sharedPrefs);

// no use context

for example, for getValidToken(Context context), the test could be:

@Before
public void before() throws Exception {
    this.sharedPrefs = Mockito.mock(SharedPreferences.class);
    this.context = Mockito.mock(Context.class);
    Mockito.when(context.getSharedPreferences(anyString(), anyInt())).thenReturn(sharedPrefs);
}

@Test
public void testGetValidToken() throws Exception {
    Mockito.when(sharedPrefs.getString(anyString(), anyString())).thenReturn("foobar");
    assertEquals("foobar", Auth.getValidToken(context));
    // maybe add some verify();
}

There is a better way to mock SharedPreferences, IMHO. I like Mockito, but it is unproductive to mock SharedPreferences in every test.

Luckily, we can use the shared-preferences-mock library. This library implements SharedPrefences on JVM, so it behaves like a real class. Moreover, it is possible to write local unit tests.

For your case:

import com.github.ivanshafran.sharedpreferencesmock.SPMockBuilder;

class Test {
    private Context context;
    private SharedPreferences sharedPreferences;

    @Before
    public void setUp() {
        this.sharedPreferences = new SPMockBuilder().createSharedPreferences();
        this.context = Mockito.mock(Context.class);         
        Mockito.when(context.getSharedPreferences(Constants.LOGGED_USER_PREFERENCES,0))
            .thenReturn(sharedPreferences);
    }

    @Test
    public void test() {
        sharedPreferences.edit().putString(Constants.LOGGED_USERNAME, "admin").commit();
        String value = Auth.getLoggedUser(context);
        asssertEquals("admin", value);
    }

}

Add it to your root build.gradle at the end of repositories:

allprojects {
    repositories {
        maven { url 'https://jitpack.io' }
    }
}

Add the dependency:

dependencies {
    testImplementation 'com.github.IvanShafran:shared-preferences-mock:1.0'
}

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);
}