为什么使用 Mockito 进行 JUnit 测试而不定义"when"方法？

Question

我正在尝试测试一个数据库为空/数据库未返回任何内容的场景。

我用mockito写了一个junit4测试课。mockito创建了一个服务类和dao类。一开始，我定义了"when"方法，它起作用了。后来，我尝试调用"when"方法，看看会发生什么，但它仍然有效。为什么？

当调用myService.getDistinctObjectList((时，类myService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伪结果。如果在未配置myDao.someMethod((的情况下调用它，会发生什么？MyDao应该使用数据库，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。(我把它们简化了，MyDao有四种方法可以检索四种对象(

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

除非显式更改mock的默认行为，否则它将返回"漂亮的值"。对于集合，默认返回值是一个空集合，因此您不需要像注释掉的代码那样显式使用when调用来返回此类空集合。

Answer 2

如果myDao.someMethod((未被调用会发生什么配置？

使用纯mockito(因此没有调用读取方法的间谍用法(，它不会抛出任何异常或错误，它只会将方法实现为一个空体。然后，如果该方法被声明为void，则不需要额外的行为；如果该方法是用返回类型声明的，则它将返回声明的类型结果的默认值，该值是对象的null引用，但对于Mockito返回它们的空实例的集合，并且最后返回基元的默认值。

但请注意，Mockito的这一功能通常不会在测试逻辑中造成任何副作用，因为通常您希望断言列表的内容，而不仅仅是它们的非无效性
但在您的情况下，您模拟空列表：

when(myDao.listSomeObjectTypeB()).thenReturn( Collections.<SomeObjectTypeB>emptyList() );