In this post under Mockito, I will show how to create a mock of an interface with an example

Below is the complete example where I create a mock of java.util.List interface and call its method.

Test Class

1  package package3;
2  
3  import static org.junit.Assert.assertEquals;
4  import static org.mockito.Mockito.when;
5  
6  import java.util.List;
7  
8  import org.junit.Test;
9  import org.mockito.Mockito;
10 
11 public class ListTest {
12  @Test
13  public void testListAdd() {
14      List list = Mockito.mock(List.class);
15      when(list.get(0)).thenReturn(1);
16      when(list.get(1)).thenReturn(2);
17      
18      assertEquals(1, list.get(0));
19      assertEquals(2, list.get(1));
20  }
21 }

In the above code, at line 14, we create a mock of List interface by calling Mockito class’s mock method.

In this way we can mock an interface.