在JUnit测试中模拟Dateformat(SimpleDateFormat)

问题描述 投票:0回答:2

我试图测试使用DateFormat(SimpleDateFormat)的DAO函数。当我尝试运行测试即时获取:

java.lang.NullPointerException
    at java.util.Calendar.setTime(Calendar.java:1770)
    at java.text.SimpleDateFormat.format(SimpleDateFormat.java:943)
    at java.text.SimpleDateFormat.format(SimpleDateFormat.java:936)
    at java.text.DateFormat.format(DateFormat.java:345)

这指向:election.setStartDate(df.format(rs.getDate(“startDate”)));在DAO

这是测试代码:

@RunWith(MockitoJUnitRunner.class)
public class AdminDaoImplTest {

    @Mock
    Connection mockConn;
    @Mock
    PreparedStatement mockPreparedStmnt;
    @Mock
    ResultSet mockResultSet;

    @Mock
    DateFormat formatter;

    @InjectMocks
    private AdminDao adminDao = new AdminDaoImpl();

    @Mock
    private SQLConnection mockSqlConnection;

    @BeforeClass
    public static void setUpClass() throws Exception {
    }

    @AfterClass
    public static void tearDownClass() {
    }

    @Before
    public void init() throws SQLException {
        when(mockSqlConnection.getConnection()).thenReturn(mockConn);
        when(mockConn.prepareStatement(anyString())).thenReturn(mockPreparedStmnt);
        when(mockPreparedStmnt.executeQuery()).thenReturn(mockResultSet);
        when(mockResultSet.next()).thenReturn(Boolean.TRUE, Boolean.FALSE);
when(formatter.format(any())).thenReturn("'2018-11-12 00:00'");
    }

    @After
    public void tearDown() {
    }

    @Test
    public void testGetElectionsNoExceptions() throws SQLException {

        ElectionListResponse electionListResponse = new ElectionListResponse();

        adminDao.getElections('>' );

        //verify and assert
        verify(mockConn, times(1)).prepareStatement(anyString());
        verify(mockPreparedStmnt, times(1)).executeQuery();
        verify(mockResultSet, times(1)).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");
    }
}

这是DAO中的功能:

@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;
    }

我已经尝试了一些我在网上找到的例子,但我仍然得到同样的错误。我也读过DateFormat是一个最终函数,不能被模拟。有一些解决方法,但对我不起作用。我不确定我是否正确实施了这些解决方法。

能否请您提供修复此NullPointer的代码?提前致谢!

java unit-testing junit mockito simpledateformat
2个回答
1
投票

首先,我没有看到任何模拟rs.getDate()的东西,所以它将返回null。这可能会导致SimpleDateFormat的模拟和真实实例出现问题。你可以这样解决:

// (I am using the deprecated constructor for simplicity)
java.sql.Date startDate = new java.sql.Date(2018, 6, 5);
Mockito.when(mockResultSet.getDate("startDate")).thenReturn(startDate);

结合when(formatter.format(any())).thenReturn("'2018-11-12 00:00'")可能会让你超越异常。但是,看起来,就像你在SimpleDateFormat中创建一个真正的AdminDaoImpl而你的嘲笑根本就不会被使用。因此,您必须修改AdminDaoImpl以允许您注入SimpleDateFormat或编写测试,以便他们不知道AdminDaoImpl使用SimpleDateFormat

就个人而言,我根本不会嘲笑SimpleDateFormat。相反,我会将其视为AdminDaoImpl的内部实现细节。我会模拟结果集以返回日期,然后验证ElectionListResponse是否具有预期日期。这看起来像这样:

// (I am using the deprecated constructor for simplicity)
java.sql.Date startDate = new java.sql.Date(2018, 6, 5);
Mockito.when(mockResultSet.getDate("startDate")).thenReturn(startDate);
ElectionListResponse response = adminDao.getElections('>' );
Election firstElection = response.getFirst() // Or whatever method(s) get you the first one
Assert.assertEquals("2018-06-05 00:00", firstElection.getStartDate());

这些测试证实Election从结果集中正确映射了startDate,但他们并不关心AdminDaoImpl是如何做到的。


0
投票

如果您正在模拟DateFormat,那么为什么要创建SimpleDateFormat对象。您应该在使用SimpleDateFormat对象的任何地方提供when()和thenReturn()。应该模拟所有依赖项,不存在实际的对象创建。

在DAO的单元测试中没有数据库交互,您可以轻松地模拟数据库层。

when(df.format("your_date").thenReturn(some_value);
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