title: Testing with UI elements in Android view
body: <p>I am attempting to test simple UI with the following test case,
  The main idea is to set in the test some of the UI text (to mimic user input) and then actively click an event.</p>
  
  <pre><code>public class StackTestCase 
  extends ActivityInstrumentationTestCase2&lt;Stack&gt; 
  {
  private StackDemo mActivity;
  
  private EditText eaten;
      public StuckTestCase() {
           super("com.crocodil.software.stack", Stack.class);
  
  
      }
      public StuckTestCase(Class&lt;Stack&gt; activityClass) {
           super("com.crocodil.software.stack", activityClass);
  
      }
      protected void setUp() throws Exception {
          super.setUp();
          mActivity = this.getActivity();
          mCount = (Button) mActivity.findViewById(com.crocodil.software.stack.R.id.action);
          eaten = (EditText) mActivity.findViewById(com.crocodil.software.stack.R.id.eaten);
  
      }
  
      public void testPreconditions() {
          assertNotNull(mStatus);
        }
  
      public void testSimpleDefaults(){
          double status = Double.valueOf(mStatus.getText().toString());
          eaten.setText(2);
          mCount.performClick();
          assertEquals((status-2),Double.valueOf(mStatus.getText().toString()));
      }
  
  }
  </code></pre>
  
  <p>the running result is the exception - </p>
  
  <pre><code>android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
  at android.view.ViewRoot.checkThread(ViewRoot.java:2802)
  at android.view.ViewRoot.playSoundEffect(ViewRoot.java:2581)
  at android.view.View.playSoundEffect(View.java:8516)
  at android.view.View.performClick(View.java:2407)
  at com.crocodil.software.stack.test.StackTestCase.testSimpleDefaults(StackTestCase.java:46)
  at java.lang.reflect.Method.invokeNative(Native Method)
  at android.test.InstrumentationTestCase.runMethod(InstrumentationTestCase.java:204)
  at android.test.InstrumentationTestCase.runTest(InstrumentationTestCase.java:194)
  at android.test.ActivityInstrumentationTestCase2.runTest(ActivityInstrumentationTestCase2.java:186)
  at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:169)
  at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:154)
  at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:520)
  at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1447)
  </code></pre>
  
  <p>This happens on each access to the UI elements and i was unable to avoid it by using handles or async task ? any suggestions?</p>