A Minimalist Guide to Setting Up Unit Tests in Spring Boot

This article provides a minimalist unit‑testing method aimed at beginners, showing how to create a functional unit‑testing environment with only the necessary Maven dependencies and test classes in a locally runnable Spring Boot project.

Contents include:

POM dependencies

Unit‑test class examples

Unit‑testing experience summary

POM dependencies

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-test</artifactId>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.mockito</groupId>
  <artifactId>mockito-core</artifactId>
  <version>3.12.4</version>
</dependency>

1. Integration‑style unit tests – require the application context to start and may connect to databases or RPC registries. Key annotations:

@SpringBootTest + @RunWith(SpringRunner.class) – launch a Spring Boot test environment.

@Transactional – rolls back database changes after each test.

@Resource – inject the class under test.

@SpyBean – mock beans within the Spring context.

@Test – mark a test method.

Example:

/**
 * @author jiangbo8
 * @since 2024/4/24 9:52
 */
@Transactional
@SpringBootTest
@RunWith(SpringRunner.class)
public class SalesAmountPlanControllerAppTest {
    @Resource
    private SalesAmountPlanController salesAmountPlanController;
    @SpyBean
    private ISaleAmountHourHistoryService saleAmountHourHistoryServiceImpl;
    @SpyBean
    private ISaleAmountHourForecastService saleAmountHourForecastServiceImpl;
    @SpyBean
    private ISaleAmountHourPlanService saleAmountHourPlanServiceImpl;

    @Test
    public void testGraph1()  {
        // real call without mock
        SalesAmountDTO dto = new SalesAmountDTO();
        dto.setDeptId1List(Lists.newArrayList(35));
        dto.setDeptId2List(Lists.newArrayList(235));
        dto.setDeptId3List(Lists.newArrayList(100));
        dto.setYoyType(YoyTypeEnum.SOLAR.getCode());
        dto.setShowWeek(true);
        dto.setStartYm("2024-01");
        dto.setEndYm("2024-10");
        dto.setTimeDim(GraphTimeDimensionEnum.MONTH.getCode());
        dto.setDataType(SalesAmountDataTypeEnum.AMOUNT.getCode());
        Result<ChartData> result = salesAmountPlanController.graph(dto);
        System.out.println(JSON.toJSONString(result));
        Assert.assertNotNull(result);
    }

    @Test
    public void testGraph11()  {
        // mock behavior
        Mockito.doAnswer(this::mockSaleAmountHourHistoryListQuery)
               .when(saleAmountHourHistoryServiceImpl).listBySaleAmountQueryBo(any());
        Mockito.doAnswer(this::mockSaleAmountHourPlansListQuery)
               .when(saleAmountHourPlanServiceImpl).listBySaleAmountQueryBo(any());
        Mockito.doAnswer(this::mockSaleAmountHourForecastListQuery)
               .when(saleAmountHourForecastServiceImpl).listBySaleAmountQueryBo(any());
        // ... (rest of test setup)
        Result<ChartData> result = salesAmountPlanController.graph(dto);
        System.out.println(JSON.toJSONString(result));
        Assert.assertNotNull(result);
    }

    private List<SaleAmountHourHistory> mockSaleAmountHourHistoryListQuery(org.mockito.invocation.InvocationOnMock s) {
        // mock implementation returning fabricated data
        // ... (omitted for brevity)
        return historyList;
    }
}

2. Pure unit tests – do not start the Spring context and avoid external dependencies; all collaborators are mocked. Key annotations:

@InjectMocks – creates the class under test and injects @Mock fields.

@Mock – defines mock collaborators.

@Test – marks a test method.

Example:

/**
 * Created by jiangbo8 on 2022/10/17 15:02
 */
public class CheckAndFillProcessorTest {
    @Mock Logger log;
    @Mock OrderRelService orderRelService;
    @Mock VenderServiceSdk venderServiceSdk;
    @Mock AfsServiceSdk afsServiceSdk;
    @Mock PriceServiceSdk priceServiceSdk;
    @Mock ProductInfoSdk productInfoSdk;
    @Mock OrderMidServiceSdk orderMidServiceSdk;
    @Mock OrderQueueService orderQueueService;
    @Mock SendpayMarkService sendpayMarkService;
    @Mock TradeOrderService tradeOrderService;

    @InjectMocks
    CheckAndFillProcessor checkAndFillProcessor;

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

    @Test
    public void testProcess2() throws Exception {
        OrderRel orderRel = new OrderRel();
        orderRel.setSopOrderId(1111111L);
        orderRel.setVenderId("123");
        when(orderRelService.queryOrderBySopOrderId(anyLong())).thenReturn(orderRel);
        // additional mock setups omitted for brevity
        OrderQueue orderQueue = new OrderQueue();
        orderQueue.setSopOrderId(1111111L);
        DispatchResult result = checkAndFillProcessor.process(orderQueue);
        Assert.assertNotNull(result);
    }
}

3. Unit‑testing experience summary

The author shares practical scenarios where unit tests add value: during refactoring, they provide a safety net to verify behavior unchanged; for new features, a mix of integration‑style and pure unit tests balances coverage and effort; and the emphasis is on quality over raw coverage metrics.

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