Mock Android Context using Mockito

mock_android_context.java

import org.mockito.Mock;
import static org.mockito.Mockito.when;

@Mock
private Context mockApplicationContext;
@Mock
private Resources mockContextResources;
@Mock
private SharedPreferences mockSharedPreferences;

@Before
public void setupTests() {
    // Mockito has a very convenient way to inject mocks by using the @Mock annotation. To
    // inject the mocks in the test the initMocks method needs to be called.
    MockitoAnnotations.initMocks(this);

    // During unit testing sometimes test fails because of your methods
    // are using the app Context to retrieve resources, but during unit test the Context is null
    // so we can mock it.

    when(mockApplicationContext.getResources()).thenReturn(mockContextResources);
    when(mockApplicationContext.getSharedPreferences(anyString(), anyInt())).thenReturn(mockSharedPreferences);

    when(mockContextResources.getString(anyInt())).thenReturn("mocked string");
    when(mockContextResources.getStringArray(anyInt())).thenReturn(new String[]{"mocked string 1", "mocked string 2"});
    when(mockContextResources.getColor(anyInt())).thenReturn(Color.BLACK);
    when(mockContextResources.getBoolean(anyInt())).thenReturn(false);
    when(mockContextResources.getDimension(anyInt())).thenReturn(100f);
    when(mockContextResources.getIntArray(anyInt())).thenReturn(new int[]{1,2,3});
    // here you can mock additional methods ...  

    // if you have a custom Application class, you can inject the mock context like this
    MyCustomApplication.setAppContext(mockApplicationContext);
}

Please add mock
when(mockApplicationContext.getApplicationContext()).thenReturn(mockApplicationContext);

Can you mock a getString with placeHolder?

Could you give example of MyCustomApplication please?

Could you give example of MyCustomApplication please?

@l225li MyCustomApplication is simply an Application subclass like this (in Kotlin):

class TDFApplication : Application() { override fun onCreate(){} }

remember to declare your custom application class into the Manifest.xml file like this:

<manifest> ... <application android:name=".MyCustomApplication"> ...

Thank you @marcouberti!

A depracation note on initMocks:

@deprecated public static void initMocks (Object testClass) Deprecated.
Use openMocks(Object) instead.