Android Testing Fundamentals Question

I. Android instrumentation ?
Android instrumentation is a set of control methods to control an Android component independently of its normal life cycle. They also control how Android loads applications.

android instrumentation can load both a test package and the application under test into the same process. Since the application components and their tests are in the same process, the tests can invoke methods in the components, and modify and examine fields in the components.

Normally, an Android component runs in a lifecycle determined by the system. For example, an Activity object's lifecycle starts when the Activity is activated by an Intent. The object's onCreate() method is called, followed by onResume(). When the user starts another application, the onPause() method is called. If the Activity code calls the finish() method, the onDestroy() method is called. The Android framework API does not provide a way for your code to invoke these callback methods directly, but you can do so using instrumentation.
Also, the system runs all the components of an application into the same process. You can allow some components, such as content providers, to run in a separate process, but you can't force an application to run in the same process as another application that is already running.
With Android instrumentation, though, you can invoke callback methods in your test code. This allows you to run through the lifecycle of a component step by step, as if you were debugging the component. The following test code snippet demonstrates how to use this to test that an Activity saves and restores its state:

    // Start the main activity of the application under test
    mActivity = getActivity();

    // Get a handle to the Activity object's main UI widget, a Spinner
    mSpinner = (Spinner)mActivity.findViewById(com.android.example.spinner.R.id.Spinner01);

    // Set the Spinner to a known position
    mActivity.setSpinnerPosition(TEST_STATE_DESTROY_POSITION);

    // Stop the activity - The onDestroy() method should save the state of the Spinner
    mActivity.finish();

    // Re-start the Activity - the onResume() method should restore the state of the Spinner
    mActivity = getActivity();

    // Get the Spinner's current position
    int currentPosition = mActivity.getSpinnerPosition();

    // Assert that the current position is the same as the starting position
    assertEquals(TEST_STATE_DESTROY_POSITION, currentPosition);

II. Test Case Classes

 1.AndroidTestCase:

   It extend both TestCase and Assert. It provides the
   JUnit-standard setUp() and tearDown() methods, as well as well as
   all of JUnit's Assert methods. In addition, it provides methods for testing permissions, and a
   method that guards against memory leaks by clearing out certain class references. 

This test case provides a framework in which you can test Application classes in
   a controlled environment.

Class Overview: Extend this if you need to access Resources or other things that depend on Activity Context.

http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/2.2_r1.1/android/test/AndroidTestCase.java 

 2.ApplicationTestCase

The test case can be useful in verifying that the <application> element in the manifest file is correctly
    set up. Note, however, that this test case does not allow you to control testing of the
    components within your application package.

3.InstrumentationTestCase

for testing some part of the activity in isolation

4.MockObjectClass

      Mock Context class implements all methods in a non-functional way and throw    UnsopportedOperationException.
   This can be used to inject other dependencies, mocks, or monitors into the classes under testing. A fine control can be obtained extending this class.
   Extend this class to provide your desired behaviour overriding the correspondent methods.
   This document can be read in Google Docs : https://docs.google.com/View?id=ddwc44gs_21737cgtvfj

full details can be read at: http://developer.android.com/guide/topics/testing/testing_android.html