assertEquals - always pass test - Android Studio

I'm new on junit test. I do not understand where I'm wrong. here is a simple unit tests (which simplifies my real test):

import android.test.InstrumentationTestCase;
public class exampleTest extends InstrumentationTestCase {
    String ob1, ob2;

    public void setUp() throws Exception {
        super.setUp();
        ob1 = "hi";
        ob2 = "bye";
    }

   public void  testEx()throws Exception{
       assertEquals("Error", ob1, ob2);
   }
}

When I run exampleTest I get that the test always passes.

Where i'm wrong? can someone explain me?