Mockito is a mocking framework. It goes further than JUnit by allowing you to test the interactions between objects without having to replicate the entire environment. You can read more about Mockito at its project site, https://code.google.com/p/mockito/.

You can use Mockito to do unit testing on smaller units. For instance, you can mock a org.apache.hadoop.hbase.Server instance or a org.apache.hadoop.hbase.master.MasterServices interface reference rather than a full-blown org.apache.hadoop.hbase.master.HMaster.

This example builds upon the example code in Chapter 19, Unit Testing HBase Applications, to test the insertRecord method.

First, add a dependency for Mockito to your Maven POM file.

<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-all</artifactId>
    <version>1.9.5</version>
    <scope>test</scope>
</dependency>                   
                   

Next, add a @RunWith annotation to your test class, to direct it to use Mockito.

@RunWith(MockitoJUnitRunner.class)
public class TestMyHBaseDAO{
  @Mock 
  private HTableInterface table;
  @Mock
  private HTablePool hTablePool;
  @Captor
  private ArgumentCaptor putCaptor;

  @Test
  public void testInsertRecord() throws Exception {
    //return mock table when getTable is called
    when(hTablePool.getTable("tablename")).thenReturn(table);
    //create test object and make a call to the DAO that needs testing
    HBaseTestObj obj = new HBaseTestObj();
    obj.setRowKey("ROWKEY-1");
    obj.setData1("DATA-1");
    obj.setData2("DATA-2");
    MyHBaseDAO.insertRecord(table, obj);
    verify(table).put(putCaptor.capture());
    Put put = putCaptor.getValue();
  
    assertEquals(Bytes.toString(put.getRow()), obj.getRowKey());
    assert(put.has(Bytes.toBytes("CF"), Bytes.toBytes("CQ-1")));
    assert(put.has(Bytes.toBytes("CF"), Bytes.toBytes("CQ-2")));
    assertEquals(Bytes.toString(put.get(Bytes.toBytes("CF"),Bytes.toBytes("CQ-1")).get(0).getValue()), "DATA-1");
    assertEquals(Bytes.toString(put.get(Bytes.toBytes("CF"),Bytes.toBytes("CQ-2")).get(0).getValue()), "DATA-2");
  }
}                   
               

This code populates HBaseTestObj with “ROWKEY-1”, “DATA-1”, “DATA-2” as values. It then inserts the record into the mocked table. The Put that the DAO would have inserted is captured, and values are tested to verify that they are what you expected them to be.

The key here is to manage htable pool and htable instance creation outside the DAO. This allows you to mock them cleanly and test Puts as shown above. Similarly, you can now expand into other operations such as Get, Scan, or Delete.