How to mock jdbcTemplate call of DAO class for Junit test - junit

Question

I have DAO class as below:-
// Here I have a class that creates it's own jdbcTemplate using new
// jdbcTemplate(dataSource)
#Repository
public class MyDao {
#Autowired
#Qualifier("db2JdbcTemplate)"
JdbcTemplate jdbcTemplateDB2;
public int insertTable(Company comp) {
int ret = 0;
try {
ret = this.jdbcTemplateDB2(db2DataSource).update(ïnsert into "+ table_name + "(COL1,COL2,...) values (?,?,?,..)",
ps-> {
ps.setString(1, comp.getName);
.......
});
return ret;
} catch (Exception ex) {
// log etc
}
}
}
My Test class is as below:-
#RunWith(MockitoJUnitRunner.class)
public class MyTest {
#Mock
JdbcTemplate jdbcTemplateDB2;
Company comp = new Company(); // this is followed by setter fn to set values.
MyDao mydao = Mockito.mock(MyDao.class);
Mockito.when(((jdbcTemplateDB2.update(any(String.class),
any(PreparedStatement.class))).thenReturn(2);
ReflectionUtils.setField(mydao, "jdbcTemplateDB2", jdbcTemplateDB2);
int bVal = mydao.insertTable(cmp);
}
}
iVal is not getting value 2. It is making original update call and returning value like 0/1.
Getting UnnecessaryStubbingException. If I make lenient() call the exception goes away but result is same (expected as lenient only removes warning).
How to make this stubbing work?

Answer 1

In this line: MyDao mydao = Mockito.mock(MyDao.class); you're creating a mock object, which overrides your actual class'x behavior, but you seem to want to test this very class, so it doesn't make any sense. What you need to do is: create an actual instance of the class and inject mocks into it (you're using ReflectionUtils to do that, but Mockito has it's own, simple mechanism to do that).
#Mock
JdbcTemplate jdbcTemplateDB2;
// this tells mockito to create the object and inject mocks into it
#InjectMocks
MyDao myDao;
#Test
void test() {
// define the behavior for the mock
when(jdbcTemplateDB2.update(...)).thenReturn(2);
// call the actual method of the tested class object (not a mock)
int result = myDao.insertTable(...);
// perform assertions (e.g. verify the result value)
}
Recommended reading: Mockito documentation (very comprehensive, yet simple).
Important note: field injection is discouraged.