@Test
public void add()
{

    final Attribute attribute1 = new Attribute();
    final Attribute attribute2 = new Attribute();
    final Attribute attribute3 = new Attribute();
    final Category category1 = new Category();
    final Category category2 = new Category();
    container.add( attribute1 );
    container.add( attribute2 );
    container.add( attribute3 );
    container.add( category1 );
    container.add( category2 );
    Assert.assertEquals( (Integer) 0, container.mergeObjectIndex( attribute1 ) );
    Assert.assertEquals( (Integer) 1, container.mergeObjectIndex( attribute2 ) );
    Assert.assertEquals( (Integer) 2, container.mergeObjectIndex( attribute3 ) );
    Assert.assertEquals( (Integer) 0, container.mergeObjectIndex( category1 ) );
    Assert.assertEquals( (Integer) 1, container.mergeObjectIndex( category2 ) );
}