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

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'
}