Android - How can I mock a lack of camera when testing my app?

Question

I would like to check that my app shows an error message when the device it is running on has no camera. I have tried passing in a mock context but mockito gives an error when I try to mock the CameraManager class as it is declared final. Surely android has a simple solution for this? Here's my attempt:

public class CreateNewIdentityActivityUnitTest extends ActivityUnitTestCase<CreateNewIdentityActivity> {
    public CreateNewIdentityActivityUnitTest() {
        super(CreateNewIdentityActivity.class);
    }

    public void testErrorMessageDisplayedWhenNoCamerasExist() throws Exception {
        // Create the mock cameramanager
        // THIS LINE FAILS BECAUSE CAMERAMANAGER IS FINAL
        CameraManager mockCameraManager = mock(CameraManager.class);
        String[] cameraIdList = {};
        when(mockCameraManager.getCameraIdList()).thenReturn(cameraIdList);

        // Create the mock context
        Context mockContext = mock(Context.class);
        when(mockContext.getSystemService(Context.CAMERA_SERVICE)).thenReturn(mockCameraManager);

        // Start the activity
        Intent intent = new Intent(mockContext, CreateNewIdentityActivity.class);
        Activity activity = startActivity(intent, null, null);

        // Verify that the error message was made visible
        TextView errorTextView = (TextView)activity.findViewById(R.id.ErrorTextView);
        assertNotNull(errorTextView);
        assertEquals(View.VISIBLE, errorTextView.getVisibility());
    }
}

Answer 1

Unfortunately, you can't mock final class.

There're few options/hacks:

• Try to add Robolectric library and write test with it's ShadowCamera
• Move logic related to CameraManager into a separate class and inject it in Activity. Then in the Test project, you can override this injection.

• Pretty similar idea - create an interface OnCameraManagerInterface

  public interface OnCameraManagerInterface {
       String[] getListOfCameras() throws CameraAccessException;
  }
  

  Then implement it in the Activity:

  public class CreateNewIdentityActivity extends AppCompatActivity
          implements OnCameraManagerInterface {
      .......
      @TargetApi(Build.VERSION_CODES.LOLLIPOP)
      @Override
      public String[] getListOfCameras() throws CameraAccessException {
          return ((CameraManager)getSystemService(Context.CAMERA_SERVICE)).
                    getCameraIdList();
      }
  }
  

  And in the code, where you check camera existence - call: if (getListOfCameras().length == 0) {}

  Now, add new TestCreateNewIdentityActivity to override your CreateNewIdentityActivity:

   public class TestCreateNewIdentityActivity extends CreateNewIdentityActivity {
      @Override
      public String[] getListOfCameras() throws CameraAccessException {
          return new String[0];
      }
  }
  

  In Manifest:

  <activity android:name=".TestCreateNewIdentityActivity"
          android:theme="@style/AppTheme.NoActionBar"/>
  

  And test will look like:

  public class CreateNewIdentityActivityUnitTest extends ActivityUnitTestCase<TestCreateNewIdentityActivity> {
      public CreateNewIdentityActivityUnitTest() {
          super(TestCreateNewIdentityActivity.class);
      }
  
      public void testErrorMessageDisplayedWhenNoCamerasExist() throws Exception {
          // Verify that the error message was made visible
          TextView errorTextView = (TextView)getActivity().findViewById(R.id.ErrorTextView);
          assertNotNull(errorTextView);
          assertEquals(View.VISIBLE, errorTextView.getVisibility());
      }
  }   
  

  I'm pretty sure, it doable even without adding the TestActivity into the main source code and to manifest(to keep it in androidTest, though I didn't look)

• Hybrid variant without creation of new activity:

      public class ActivityCameraManager {
  
      private boolean isTest = false;
      private CameraManager cameraManager;
  
      public ActivityCameraManager(CameraManager cameraManager) {
          this.cameraManager = cameraManager;
      }
  
      @TargetApi(Build.VERSION_CODES.LOLLIPOP)
      public String[] getListOfCameras() throws CameraAccessException {
          if (isTest) {
              return new String[0];
          }
  
          return cameraManager.getCameraIdList();
      }
  
      public void setTestMode() {
          isTest = true;
      }
  }
  

  Then your activity is gonna look like:

      public class MainActivity extends AppCompatActivity  {
  
      ActivityCameraManager activityCameraManager;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          ...
          activityCameraManager = new ActivityCameraManager((CameraManager) getSystemService(Context.CAMERA_SERVICE));
      }
  
      public void setActivityCameraManagerForTest() {
          activityCameraManager.setTestMode();
      }
  }
  

  And in test just call getActivity().setActivityCameraManagerForTest();

I hope, it helps

Answer 2

The answer is late but here is a mock camera example for Android.

You can set the VideoFileInputSource to mock camera from video file

textureVideoInputSource = new VideoFileInputSource(this, "mock_input_video.mp4");

or you can enable hardware camera for video stream.

textureVideoInputSource = new CameraTextureVideoInputSource(this);

You can refer the answer here. https://stackoverflow.com/a/38456189/1053097