Mockito test for getters that is inside and outside if condition

I am trying to write a Mockito test for a method as below:

public void m() {

    Entity e= this.dao.getEntity(ID);
    if(e == null) {
        //some code here
        Entity e = this.dao.getEntity(ID);
        //prepare e;
        this.dao.merge(e);
    }
}

Now how do I get inside if condition?