@Test
  public void testResturnsNullIfAppAndVersionNotFound() throws Exception {
    JSONObject jsonSource = new JSONObject();
    jsonSource.put("aut", "io.selendroid.test:0.13.0");

    SelendroidCapabilities capa = new SelendroidCapabilities(jsonSource);

    String defaultApp = capa.getDefaultApp(supportedApps);
    Assert.assertNull(defaultApp);
  }
Makes sure that the new function "getDefaultApp" will return the correct application under test from the apps store
or peacefully returns null if the app is not in the apps store. If the laucch activity is also specified with appName
then just return the appName so it can be installed to the apps store.

The tests will cover these scenarios:
<ul>

<li>If app does not exists in the apps store and the launch activity is specified, then just return
the request string as app under test so it can be installed to the device by the SelendroidStandaloneDriver. </li>
<li>If app does not exists in the appstore, and the launch activity is not specified then return null.</li>
<li>If appName and appVersion are specified then return the app under test as "appName:appVersion" if it is found in the
apps store or null if it is not.</li>
<li>If appName is specified but not the appVersion then return the latest version of the apps in the apps store as app
under test in the format of "appName:appVersion" or null if app is not found in apps store.</li>
</li>
<ul>
selendroid-common/src/test/java/io/selendroid/common/SelendroidCapabilitiesGetDefaultAppTest.java