ApplicationContext failed to load - spring-boot

Question

I am new to testing. I have created a test case to perform a test on rest API using JUNIT Mockito. In my code I have created a test on method itemGetByid(), but when I run the test I get ApplocationContext error message. I don't know where I am going wrong.
Item Controller Test class
package com.example.demo.controller;
import com.example.demo.entities.Item;
import com.example.demo.entities.User;
import com.example.demo.service.ItemService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.stubbing.Answer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.test.web.servlet.MockMvc;
import java.util.*;
import static org.junit.Assert.*;
#RunWith(SpringJUnit4ClassRunner.class)
#WebMvcTest(ItemController.class)
public class ItemControllerTest {
#Autowired
MockMvc mockmvc;
#Mock
ItemService itemService;
#InjectMocks
ItemController itemController;
#Test
public void itemGetById() {
Item item = new Item();
Mockito.when(itemController.getById(10L)).thenReturn(item);
Item i = itemController.getById(10L);
assertEquals(i, item);
}
}
Item entity class
package com.example.demo.entities;
import lombok.Data;
import javax.persistence.*;
#Data
#Entity
#Table(name = "Item")
public class Item {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long itemId;
private Long customerId;
private String itemName;
private int itemPrice;
}
Item controller
package com.example.demo.controller;
import com.example.demo.entities.Item;
import com.example.demo.entities.User;
import com.example.demo.service.ItemService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
#RestController
#RequestMapping("item")
public class ItemController {
private ItemService itemService;
#Autowired
public ItemController(ItemService itemService) {
this.itemService = itemService;
}
#PostMapping("/post")
public Item post(#RequestBody Item item) {
return itemService.post(item);
}
#GetMapping
public Iterable<Item> getAll() {
return itemService.get();
}
#GetMapping("/get")
public Item getById(Long id) {
return itemService.getItem(id);
}
#DeleteMapping("/delete")
public void deleteAll() {
itemService.deleteAll();
}
}
Item Service
package com.example.demo.service;
import com.example.demo.entities.Item;
import com.example.demo.userepository.ItemRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.RequestBody;
#Service
public class ItemService {
ItemRepository itemRepository;
#Autowired
public ItemService(ItemRepository itemRepository) {
this.itemRepository = itemRepository;
}
public Item post(#RequestBody Item item) {
return itemRepository.save(item);
}
public Iterable<Item> get() {
return itemRepository.findAll();
}
public void deleteAll() {
itemRepository.deleteAll();
}
public Item getItem(Long id) {
return itemRepository.findById(id).get();
}
}
Item Repository
package com.example.demo.userepository;
import com.example.demo.entities.Item;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
#Repository
public interface ItemRepository extends CrudRepository<Item, Long> {
}

Answer 1

For starters, you are using SpringJUnit4ClassRunner. Try the MockitoJunitRunner.
An ItemController instance is never created in the test, so that needs to be fixed as well.
The line below will fail because itemController is not a mock.
**Mockito.when(itemController.getById(10L)).thenReturn(item);**
If itemController is converted to a mock, with the when statement, the test method doesnt validate anything because the test tells Mockito to return the item in the when statement.
Assuming the intent is to validate the ItemController getById method, the Mockito.when statement needs to describe the call to the Mock ItemService.