Spring Boot implements unit testing based on JUint5

This article introduces Spring Boot 2's unit test implementation based on JUnit 5.

Introduction
Differences between JUnit 4 and JUnit 5
1. Ignore test case execution
2. RunWith Configuration
3. @Before, @BeforeClass, @After, @AfterClassIs replaced
Development environment
Example

Introduction

Spring Boot 2.2.0 version began to introduce JUnit 5 as the default library for unit testing. Before Spring Boot 2.2.0, it spring-boot-starter-testincluded the dependency of JUnit 4. After Spring Boot 2.2.0, it was replaced with Junit Jupiter.

Differences between JUnit 4 and JUnit 5

1. Ignore test case execution

JUnit 4：

@Test
@Ignore
public void testMethod() {
   // ...
}

JUnit 5：

@Test
@Disabled("explanation")
public void testMethod() {
   // ...
}

2. RunWithConfiguration

JUnit 4：

@RunWith(SpringRunner.class)
@SpringBootTest
public class ApplicationTests {
    @Test
    public void contextLoads() {
    }
}

JUnit 5：

@ExtendWith(SpringExtension.class)
@SpringBootTest
public class ApplicationTests {
    @Test
    public void contextLoads() {
    }
}

3. @Before, @BeforeClass, @After, @AfterClassis replaced

@BeforeEach replace @Before
@BeforeAll replace @BeforeClass
@AfterEach replace @After
@AfterAll replace @AfterClass

Development environment

JDK 8

Example

Create a Spring Boot project, refer to: IntelliJ IDEA to create a Spring Boot project .
Adding spring-boot-starter-webdependency, eventually pom.xmlfollows.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.6.RELEASE</version>
        <relativePath/>
    </parent>
    <groupId>tutorial.spring.boot</groupId>
    <artifactId>spring-boot-junit5</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring-boot-junit5</name>
    <description>Demo project for Spring Boot Unit Test with JUnit 5</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

After the project is created, a test class is automatically generated.

package tutorial.spring.boot.junit5;

import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
class SpringBootJunit5ApplicationTests {

    @Test
    void contextLoads() {
    }

}

The function of this test class is to check whether the application context can be started normally. @SpringBootTestAnnotation tells Spring Boot find with @SpringBootApplicationthe main configuration class notes, and use the class to start the Spring application context.

Supplement the application logic code to be tested

4.1. Define Service Layer Interface

package tutorial.spring.boot.junit5.service;

public interface HelloService {

    String hello(String name);
}

4.2. Define the Controller layer

package tutorial.spring.boot.junit5.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import tutorial.spring.boot.junit5.service.HelloService;

@RestController
public class HelloController {

    private final HelloService helloService;

    public HelloController(HelloService helloService) {
        this.helloService = helloService;
    }

    @GetMapping("/hello/{name}")
    public String hello(@PathVariable("name") String name) {
        return helloService.hello(name);
    }
}

4.3. Define the Service layer implementation

package tutorial.spring.boot.junit5.service.impl;

import org.springframework.stereotype.Service;
import tutorial.spring.boot.junit5.service.HelloService;

@Service
public class HelloServiceImpl implements HelloService {

    @Override
    public String hello(String name) {
        return "Hello, " + name;
    }
}

Write unit tests that send HTTP requests.

package tutorial.spring.boot.junit5;

import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.web.client.TestRestTemplate;
import org.springframework.boot.web.server.LocalServerPort;

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class HttpRequestTest {

    @LocalServerPort
    private int port;

    @Autowired
    private TestRestTemplate restTemplate;

    @Test
    public void testHello() {
        String requestResult = this.restTemplate.getForObject("http://127.0.0.1:" + port + "/hello/spring",
                String.class);
        Assertions.assertThat(requestResult).contains("Hello, spring");
    }
}

Description:

webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT Use a local random port to start the service;
@LocalServerPortEquivalent @Value("${local.server.port}");
In the configuration webEnvironmentafter, Spring Boot automatically provides an TestRestTemplateexample, may be used to send an HTTP request.
Except TestRestTemplateHTTP request example, the means may also org.springframework.test.web.servlet.MockMvcaccomplish similar functions, as follows:

package tutorial.spring.boot.junit5.controller;

import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
import org.springframework.test.web.servlet.result.MockMvcResultHandlers;
import org.springframework.test.web.servlet.result.MockMvcResultMatchers;

@SpringBootTest
@AutoConfigureMockMvc
public class HelloControllerTest {

    @Autowired
    private HelloController helloController;

    @Autowired
    private MockMvc mockMvc;

    @Test
    public void testNotNull() {
        Assertions.assertThat(helloController).isNotNull();
    }

    @Test
    public void testHello() throws Exception {
        this.mockMvc.perform(MockMvcRequestBuilders.get("/hello/spring"))
                .andDo(MockMvcResultHandlers.print())
                .andExpect(MockMvcResultMatchers.status().isOk())
                .andExpect(MockMvcResultMatchers.content().string("Hello, spring"));
    }
}

The above test method belongs to the overall test, that is, all application contexts are activated. There is also a layered test method, such as testing only the Controller layer.

Layered testing.

package tutorial.spring.boot.junit5.controller;

import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.Test;
import org.mockito.Mockito;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.boot.test.mock.mockito.MockBean;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;
import org.springframework.test.web.servlet.result.MockMvcResultHandlers;
import org.springframework.test.web.servlet.result.MockMvcResultMatchers;
import tutorial.spring.boot.junit5.service.HelloService;

@WebMvcTest
public class HelloControllerTest {

    @Autowired
    private HelloController helloController;

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private HelloService helloService;

    @Test
    public void testNotNull() {
        Assertions.assertThat(helloController).isNotNull();
    }

    @Test
    public void testHello() throws Exception {
        Mockito.when(helloService.hello(Mockito.anyString())).thenReturn("Mock hello");
        this.mockMvc.perform(MockMvcRequestBuilders.get("/hello/spring"))
                .andDo(MockMvcResultHandlers.print())
                .andExpect(MockMvcResultMatchers.status().isOk())
                .andExpect(MockMvcResultMatchers.content().string("Mock hello"));
    }
}

Description:

@WebMvcTestNotes tell Spring Boot only instantiated Controller layer, not to instantiate the overall context, and also further specify only instantiate an instance of the Controller layer: @WebMvcTest(HelloController.class);
Because the only example of the Controller layer, so dependent Service layer instances need to @MockBeancreate, and by Mockitothe method specified return results when Mock out of the Service layer instance method call in a particular situation.