title: Android studio says "Empty Test Suite" for AndroidTestCase
body: <p>I have created an example test case that extends AndroidTestCase. When I run the test case, 
  it errors out by saying</p>
  
  <pre><code>Running tests
  Test running startedTest running failed: 
  Instrumentation run failed due to 'java.lang.RuntimeException'
  Empty test suite.
  </code></pre>
  
  <p>The test case</p>
  
  <pre><code>import android.test.AndroidTestCase;
  import android.test.suitebuilder.annotation.SmallTest;
  
  import static org.junit.Assert.assertEquals;
  
  import org.junit.AfterClass;
  import org.junit.BeforeClass;
  import org.junit.Test;
  
  import java.lang.Exception;
  import java.lang.Override;
  
  public class DateFormatTest extends AndroidTestCase{
  
      @Override
      protected void setUp() throws Exception {
          super.setUp();
      }
  
      @Override
      protected void tearDown() throws Exception {
          super.tearDown();
      }
  
      public DateFormatTest(){
          super(DateFormatTest.class);
      }
  
  
      @SmallTest
      public void testMultiply() {
  
          assertEquals("10 x 5 must be 50", 50, 10*5);
      }
  }
  </code></pre>