Mockito

DAO.java

//Dao class
public class DAO {
 
 public Result select(Param param) {
   
   return sqlClient.select("id", param);
 }
  
}

Param.java

//Paramter class
public class Param {
 private String name;

 public void setName(String name) {
   this.name = name;
 }
 
 public String getName() {
   return name;
 }
}

Service.java

//Service
public class Service {
  
  @Autowired
  private DAO dao;
  
  public Result select() {
    
    Param param = new Param();
    return dao.select(param);
  }
}

Test.java

//TestCase

@Mock
private DAO dao;

@InjectMocks
private Service service;

@Test
public void test() {
  when(dao.select(new Param())).thenReturn(new Result());
  service.select();
  
  Assert.assertTrue(true);
}