为什么使用Mockito的JUnit测试没有定义“when”方法？

Question

我正在尝试测试一个带有空数据库/没有从数据库返回任何内容的场景。

我用mockito编写了一个junit4测试类。有一个由Mockito创建的服务类和dao类。一开始，我定义了“when”方法，它起作用了。后来，我试着拉出“when”方法调用，看看会发生什么，反正它起作用了。为什么？

当调用myService.getDistinctObjectList（）时，myService类将调用myDao的所有四个方法。所以我想我必须模拟所有四个方法并返回虚拟结果。如果MyDao.someMethod（）在未配置时被调用，会发生什么情况？MyDao应该与数据库一起工作，但我没有给它任何东西。

我附上了MyDao和MyService的示例代码以供参考。（我对它们进行了简化，MyDao有四种检索四种对象的方法）

public class MyDaoImpl implements MyDao {
    @SuppressWarnings("unused")
    private DataSource dataSource;
    private JdbcTemplate jdbcTemplate;
    private String schema;

    @ConstructorProperties({ "dataSource", "schema" })
    private MyDaoImpl(DataSource dataSource, String schema) {
        this.dataSource = dataSource;
        this.schema = schema;
        this.jdbcTemplate = new JdbcTemplate(dataSource);
    }

    @Override
    public List<SomeObjectTypeA> listSomeObjectTypeA() {
        return this.jdbcTemplate.query("select * from " + schema + ".SOME_TABLE", new RowMapper<SomeObjectTypeA>() {
            @Override
            public SoftBillAccount mapRow(ResultSet rs, int rowNum) throws SQLException {
                String memberA = rs.getString("MEMBER_A");
                String memberB = rs.getString("MEMBER_B");
            }
        });

    }
    public List<SomeObjectTypeA> listSomeObjectTypeB() {
        //omitted
    }
    public List<SomeObjectTypeA> listSomeObjectTypeC() {
        //omitted
    }
    public List<SomeObjectTypeA> listSomeObjectTypeD() {
        //omitted
    }
}

public class MyServiceImpl implements MyService {

    private MyDao myDao;

    public MyServiceImpl(){}

    @ConstructorProperties({ "myDao" })
    public MyServiceImpl(MyDao myDao) {
        this.myDao = myDao;
    }

    @Override
    public List<String> getSomeObjectTypeA_MemberA_Only() {
        List<SomeObjectTypeA> list = myDao.listSomeObjectTypeA();
        List<String> memberAList = new ArrayList<String>();
        for (SomeObjectTypeA objectA : list) {
            memberAList.add(objectA.getMemberA());
        }
        return memberAList;
    }
}



public class MyServiceImpl implements MyService {

    private MyDao myDao;

    public MyServiceImpl(){}

    @ConstructorProperties({ "myDao" })
    public MyServiceImpl(MyDao myDao) {
        this.myDao = myDao;
    }

    @Override
    public List<String> getSomeObjectTypeA_MemberA_Only() {
        List<SomeObjectTypeA> list = mydao.listSomeObjectTypeA();
        List<String> memberAList = new ArrayList<String>();
        for (SomeObjectTypeA objectA : list) {
            memberAList.add(objectA.getMemberA());
        }
        return memberAList;
    }
}

这是测试类：

public class Test1{

    @InjectMocks
    private MyServiceImpl myService;

    @Mock
    private MyDao myDao;

    @Before
    public void init() {
        MockitoAnnotations.initMocks(this);
    }

    @Test
    public void testEmptyDatabase() {

        //ArrayList<SomeObjectTypeA> list = new ArrayList<SomeObjectTypeA>();
        //list.add( new SomeObjectTypeA("A","A", "A", "A") );
        //when(myDao.listSomeObjectTypeA()).thenReturn( Collections.<SomeObjectTypeA>emptyList() );
        //when(myDao.listSomeObjectTypeB()).thenReturn( Collections.<SomeObjectTypeB>emptyList() );
        //when(myDao.listSomeObjectTypeC()).thenReturn( Collections.<SomeObjectTypeC>emptyList() );
        //when(myDao.listSomeObjectTypeD()).thenReturn( Collections.<SomeObjectTypeD>emptyList() );

        List<String> distinctList = myService.getDistinctObjectList(); // myService.getDistinctObjectList() end up calling all four methods of myDao

        //Write the List to a file, with a trailer with record count
        OutputWriter outputWriter = new OutputWriterImpl(outputFileDir, outputFilePrefix,outputFileSuffix);
        try{
            outputWriter.writeOutput(distinctList);
        }catch(IOException e){
            e.printStackTrace();
        }

        //Create a control file for comparison
        try{
            BufferedWriter bfr = new BufferedWriter(new FileWriter(compareFileDir+compareFilePrefix+compareFileSuffix));
            bfr.write("Trailer|");
            bfr.write(String.format("%07d", 0));
            bfr.newLine();
            bfr.close();
        }catch(IOException e){
            e.printStackTrace();
        }
        File file1 = new File(outputFileDir + outputFilePrefix + date + outputFileSuffix);
        File file2 = new File(compareFileDir+ compareFilePrefix+compareFileSuffix);

        System.out.println(file1.length()); // show 17
        System.out.println(file2.length()); // show 17

        assertEquals(file1.length(), file2.length());
    }

Answer 1

除非您显式地更改模拟的默认行为，否则它将返回“nice values”。对于collection，默认的返回值是空集合，因此您不需要显式地使用when调用来返回这样的空集合，就像您注释掉的代码所做的那样。