title: How to test my DAO methods using Mockito?
body: <p>I'm trying to write some tests for my DAO's. I have followed some tutorials/answers here, but most of them don't apply to my DAO's. </p>
  
  <p>Example code: trying to get the elections from the database based on the given selector (&lt; or >).</p>
  
  <pre><code>public class AdminDaoImpl extends DaoImpl implements AdminDao {
  
      private final Logger LOGGER = Logger.getLogger(getClass().getName());
  
      @Override
      public ElectionListResponse getElections(char selector) {
          ElectionListResponse electionListResponse = new ElectionListResponse();
  
          String query = NamedQueries.GET_ELECTIONS_BEGIN + selector + NamedQueries.GET_ELECTIONS_END;
  
          try {
              con = sqlConnection.getConnection();
              stmt = con.prepareStatement(query);
              rs = stmt.executeQuery();
  
              DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm");
  
              while (rs.next()) {
                  Election election = new Election();
                  election.setElectionID(rs.getInt("id"));
                  election.setElectionName(rs.getString("name"));
                  election.setStartDate(df.format(rs.getDate("startDate")));
                  election.setEndDate(df.format(rs.getDate("endDate")));
                  electionListResponse.addElection(election);
              }
              return electionListResponse;
          } catch (SQLException e) {
              LOGGER.log(Level.SEVERE, "Cant get elections. ", e);
          } finally {
              closeConnection();
          }
          return null;
      }
  </code></pre>
  
  <p>This is the DAO that the code above extends:</p>
  
  <pre><code>public abstract class DaoImpl implements Dao {
  
      private final Logger LOGGER = Logger.getLogger(getClass().getName());
  
      @Inject
      public SQLConnection sqlConnection;
  
      public Connection con;
      public PreparedStatement stmt;
      public ResultSet rs;
  
      public void closeConnection() {
          try {
              if (con != null) con.close();
              if (stmt != null) stmt.close();
              if (rs != null) con.close();
          } catch (SQLException e) {
              LOGGER.log(Level.SEVERE, "Can't close connection with database. ", e);
          }
      }
  }
  </code></pre>
  
  <p>I have tried to apply some code that I found online and this is what I currently have:</p>
  
  <pre><code>@RunWith(MockitoJUnitRunner.class)
  public class AdminDaoImplTest {
  
      @Mock
      DataSource mockDataSource;
      @Mock
      Connection mockConn;
      @Mock
      PreparedStatement mockPreparedStmnt;
      @Mock
      ResultSet mockResultSet;
  
      @BeforeClass
      public static void setUpClass() throws Exception {
      }
  
      @AfterClass
      public static void tearDownClass() {
      }
  
      @Before
      public void setUp() throws SQLException {
          when(mockDataSource.getConnection()).thenReturn(mockConn);
          when(mockDataSource.getConnection(anyString(), anyString())).thenReturn(mockConn);
          doNothing().when(mockConn).commit();
          when(mockConn.prepareStatement(anyString(), anyInt())).thenReturn(mockPreparedStmnt);
          doNothing().when(mockPreparedStmnt).setString(anyInt(), anyString());
          when(mockPreparedStmnt.executeQuery()).thenReturn(mockResultSet);
          when(mockResultSet.next()).thenReturn(Boolean.TRUE, Boolean.FALSE);
      }
  
      @After
      public void tearDown() {
      }
  
      @Test
      public void testCreateWithNoExceptions() throws SQLException {
  
          ElectionListResponse electionListResponse = new ElectionListResponse();
  
          AdminDaoImpl instance = new AdminDaoImpl();
          instance.getElections('&gt;' );
  
          //verify and assert
          verify(mockConn, times(1)).prepareStatement(anyString(), anyInt());
          verify(mockPreparedStmnt, times(1)).execute();
          verify(mockConn, times(1)).commit();
          verify(mockResultSet, times(2)).next();
          verify(mockResultSet, times(1)).getInt("id");
          verify(mockResultSet, times(1)).getString("name");
          verify(mockResultSet, times(1)).getDate("startDate");
          verify(mockResultSet, times(1)).getDate("endDate");
      }
  
  
  }
  </code></pre>
  
  <p>How should I test it ? Would you please produce some code samples? Thanks in advance!</p>
  
  <p>NullPointer:</p>
  
  <pre><code>java.lang.NullPointerException
      at org.han.ica.oose.sneeuwklokje.database.admin.AdminDaoImpl.getElections(AdminDaoImpl.java:28)
      at org.han.ica.oose.sneeuwklokje.database.admin.AdminDaoImplTest.testGetElectionsNoExceptions(AdminDaoImplTest.java:77)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
      at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
      at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
      at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
      at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
      at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
      at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
      at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
      at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
      at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
      at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
      at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
      at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
      at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
      at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
      at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
      at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
      at org.mockito.internal.runners.JUnit45AndHigherRunnerImpl.run(JUnit45AndHigherRunnerImpl.java:37)
      at org.mockito.runners.MockitoJUnitRunner.run(MockitoJUnitRunner.java:62)
      at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
      at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
      at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
      at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
      at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
  </code></pre>