Spring Boot Test Writing

Name: springboot-tests
Rating: 92
Author: JohnFattore

Stack

JUnit 5 (Jupiter) + Mockito + Spring Boot Test (spring-boot-starter-test)

File Conventions

•Tests mirror the main source tree: springboot/src/test/java/com/example/sec_api/
•Example: class com.example.sec_api.service.EdgarService → test in com/example/sec_api/service/EdgarServiceTest.java
•Reference: QuarterUtilsTest.java for plain unit test style
•Run: cd springboot && mvn test
•Run single: mvn -Dtest=EdgarServiceTest test

Test Slices

Pick the right annotation based on what you're testing:

Target	Annotation	Notes
Utility/POJO	None	Plain JUnit, no Spring context
Service	`@ExtendWith(MockitoExtension.class)`	`@Mock` + `@InjectMocks`
Controller	`@WebMvcTest(MyController.class)`	`MockMvc` + `@MockBean`
Repository	`@DataJpaTest`	In-memory DB, auto-rollback
Full integration	`@SpringBootTest`	Full context, use sparingly

Test Patterns

Utility / Plain Unit Test

java

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

class QuarterUtilsTest {
    @Test
    void parsesQuarterString() {
        assertEquals(1, QuarterUtils.parseQuarter("Q1-2024"));
    }
}

Service Test (Mockito)

java

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;
import static org.mockito.Mockito.*;
import static org.junit.jupiter.api.Assertions.*;

@ExtendWith(MockitoExtension.class)
class EdgarServiceTest {

    @Mock
    private EdgarRepository edgarRepository;

    @InjectMocks
    private EdgarService edgarService;

    @Test
    void returnsDataForValidTicker() {
        when(edgarRepository.findByTicker("AAPL")).thenReturn(List.of(mockEntity));
        var result = edgarService.getFilings("AAPL");
        assertFalse(result.isEmpty());
        verify(edgarRepository).findByTicker("AAPL");
    }
}

Controller Test (MockMvc)

java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.boot.test.mock.mockbean.MockBean;
import org.springframework.test.web.servlet.MockMvc;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;

@WebMvcTest(EdgarController.class)
class EdgarControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private EdgarService edgarService;

    @Test
    void getFilingsReturns200() throws Exception {
        when(edgarService.getFilings("AAPL")).thenReturn(List.of());
        mockMvc.perform(get("/api/edgar/filings").param("ticker", "AAPL"))
               .andExpect(status().isOk())
               .andExpect(jsonPath("$").isArray());
    }
}

Repository Test (DataJpaTest)

java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;

@DataJpaTest
class EdgarRepositoryTest {

    @Autowired
    private EdgarRepository repository;

    @Test
    void findsFilingsByTicker() {
        // Entity is auto-persisted via test data or setUp
        var results = repository.findByTicker("MSFT");
        assertFalse(results.isEmpty());
    }
}

Workflow

•Identify the class -- controller, service, repository, or utility
•Pick the test slice -- see table above; prefer the lightest annotation that works
•Mock dependencies -- @MockBean for Spring context tests, @Mock + @InjectMocks for plain Mockito
•
Write tests:
- •Happy path with valid inputs
- •Edge cases (null, empty, invalid)
- •For controllers: assert status code + JSON response structure
- •For services: verify repository/external calls with verify()
•Mirror package structure -- test class lives in the same package under src/test/java/
•Run -- cd springboot && mvn test or mvn -Dtest=ClassName test