在开发中，单元测试（Unit Testing）又称为模块测试, 是针对程序模块（软件设计的最小单位）来进行正确性检验的测试工作。程序单元是应用的最小可测试部件。简单来说，就是测试数据的稳定性是否达到程序的预期。
JUnit 是一个 Java 语言的单元测试框架。 Junit 测试是程序员测试，即所谓白盒测试，因为程序员知道被测试的软件如何（How）完成功能和完成什么样（What）的功能。Junit 是一套框架，继承 TestCase 类，就可以用 Junit 进行自动测试了。
JUnit：https://junit.org/
JUnit GitHub：https://github.com/junit-team
本文将完全复制 “ Springboot基础知识（08）- spring-boot-starter-web（Web启动器）” 里的 SpringbootWeb 项目的代码和配置到新项目 SpringbootWebJunit，并在新项目 SpringbootWebJunit 的基础上使用 Junit 测试基于 MyBatis 的数据库增删改查（CRUD）操作。
1. 导入 JDBC、MariaDB、MyBatis 等相关依赖包
访问 http://www.mvnrepository.com/ 查询依赖包。
修改 pom.xml:
1 <project ... > 2 ... 3 4 <dependencies> 5 ... 6 7 <dependency> 8 <groupId>org.mariadb.jdbc</groupId> 9 <artifactId>mariadb-java-client</artifactId> 10 </dependency> 11 <dependency> 12 <groupId>org.springframework.boot</groupId> 13 <artifactId>spring-boot-starter-data-jdbc</artifactId> 14 </dependency> 15 <dependency> 16 <groupId>org.mybatis.spring.boot</groupId> 17 <artifactId>mybatis-spring-boot-starter</artifactId> 18 <version>2.2.0</version> 19 </dependency> 20 21 <dependency> 22 <groupId>org.projectlombok</groupId> 23 <artifactId>lombok</artifactId> 24 <version>1.18.8</version> 25 </dependency> 26 27 ... 28 </dependencies> 29 30 ... 31 </project>
注：
(1) 使用 IDEA 向导创建的 "org.apache.maven.archtypes:maven-archtype-quickstart" 类型项目，会默认自动添加 JUnit 依赖包， 根据项目需要调整 JUnit 的版本，本文改成了 4.12。
(2) lombok 提供了一些简化实体类定义的注解。要使用 lombok，IDEA 需要安装 lombok 插件，这里以 Windows 版的 IDEA 为例，安装步骤如下：
菜单 File -> Settings -> 选中左侧 Plugin -> 搜索 "lombok" -> Install lombok plugin -> Restart IDEA
在 IDE 中项目列表 -> SpringbootWebJunit -> 点击鼠标右键 -> Maven -> Reload Project
2. 配置数据库(MariaDB)
1) 创建数据库 testdb 和 user 表，SQL 脚本如下
1 CREATE TABLE `user` ( 2 `id` int(11) NOT NULL AUTO_INCREMENT, 3 `username` varchar(50) NOT NULL, 4 `password` varchar(255) DEFAULT NULL, 5 `age` int(11) DEFAULT NULL, 6 `createtime` timestamp NULL DEFAULT NULL, 7 PRIMARY KEY (`id`) 8 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
2) 实体类
创建 src/main/java/com/example/entity/User.java 文件
1 package com.example.entity;
2
3 import java.util.Date;
4 import java.io.Serializable;
5
6 import lombok.Data;
7 import lombok.NoArgsConstructor;
8 import lombok.experimental.Accessors;
9
10 @NoArgsConstructor // 无参构造函数
11 @Data // 提供类的 get、set、equals、hashCode、canEqual、toString 方法
12 @Accessors(chain = true)
13 public class User implements Serializable {
14 private Integer id;
15 private String username;
16 private String password;
17 private Integer age;
18 private Date createtime;
19
20 }
3. 配置 MyBatis
1) 修改 src/main/resources/application.properties 文件
1 spring.main.banner-mode=off 2 3 # Web server 4 server.display-name=SpringBootWebJunit 5 server.address=localhost 6 server.port=9090 7 8 # 数据源配置 9 spring.datasource.username=root 10 spring.datasource.password=123456 11 spring.datasource.url=jdbc:mysql://127.0.0.1:3306/testdb 12 spring.datasource.driver-class-name=org.mariadb.jdbc.Driver 13 14 mybatis.mapper-locations=classpath:mapper/*.xml
2) 创建 src/main/java/com/example/mapper/UserMapper.java 文件
1 package com.example.mapper;
2
3 import org.apache.ibatis.annotations.Mapper;
4 import org.apache.ibatis.annotations.Param;
5
6 import com.example.entity.User;
7
8 @Mapper
9 public interface UserMapper {
10 int insert(User user);
11 int insertSelective(User user);
12
13 User selectByPrimaryKey(Integer id);
14 User selectByUsername(String username);
15
16 int updateByPrimaryKey(User user);
17 int updateByPrimaryKeySelective(User user);
18 void update(@Param("username") String username, @Param("password") String password);
19
20 int deleteByPrimaryKey(Integer id);
21 }
当 mapper 接口较多时，可以在 Spring Boot 主启动类上使用 @MapperScan 注解扫描指定包下的 mapper 接口，而不再需要在每个 mapper 接口上都标注 @Mapper 注解。
3) 创建 src/main/resources/mapper/UserMapper.xml 文件
1 <?xml version="1.0" encoding="UTF-8"?>
2 <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
3 "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
4 <mapper namespace="com.example.mapper.UserMapper">
5 <resultMap id="BaseResultMap" type="com.example.entity.User">
6 <id column="id" jdbcType="BIGINT" property="id"/>
7 <result column="username" jdbcType="VARCHAR" property="username"/>
8 <result column="password" jdbcType="VARCHAR" property="password"/>
9 <result column="age" jdbcType="INTEGER" property="age"/>
10 <result column="createtime" jdbcType="DATE" property="createtime"/>
11 </resultMap>
12 <sql id="Base_Column_List">
13 id, username, password, age, createtime
14 </sql>
15 <insert id="insert" parameterType="com.example.entity.User">
16 INSERT INTO user (id, username, password, age, createtime)
17 VALUES (#{id,jdbcType=BIGINT}, #{username,jdbcType=VARCHAR}, #{password,jdbcType=VARCHAR},
18 #{age,jdbcType=INTEGER}, #{createtime,jdbcType=DATE})
19 </insert>
20 <update id="update">
21 UPDATE user
22 SET password = #{password}
23 WHERE username = #{username}
24 </update>
25 <select id="selectByPrimaryKey" parameterType="java.lang.Long" resultMap="BaseResultMap">
26 SELECT
27 <include refid="Base_Column_List"/>
28 FROM user
29 WHERE id = #{id,jdbcType=BIGINT}
30 </select>
31 <select id="selectByUsername" parameterType="java.lang.String" resultMap="BaseResultMap">
32 SELECT
33 <include refid="Base_Column_List"/>
34 FROM user
35 WHERE username = #{username,jdbcType=VARCHAR}
36 </select>
37 <insert id="insertSelective" parameterType="com.example.entity.User">
38 INSERT INTO user
39 <trim prefix="(" suffix=")" suffixOverrides=",">
40 <if test="id != null">
41 id,
42 </if>
43 <if test="username != null">
44 username,
45 </if>
46 <if test="password != null">
47 password,
48 </if>
49 <if test="age != null">
50 age,
51 </if>
52 <if test="createtime != null">
53 createtime,
54 </if>
55 </trim>
56 <trim prefix="values (" suffix=")" suffixOverrides=",">
57 <if test="id != null">
58 #{id,jdbcType=BIGINT},
59 </if>
60 <if test="username != null">
61 #{username,jdbcType=VARCHAR},
62 </if>
63 <if test="productId != null">
64 #{password,jdbcType=VARCHAR},
65 </if>
66 <if test="age != null">
67 #{age,jdbcType=INTEGER},
68 </if>
69 <if test="createtime != null">
70 #{createtime,jdbcType=DATE},
71 </if>
72 </trim>
73 </insert>
74 <update id="updateByPrimaryKeySelective" parameterType="com.example.entity.User">
75 UPDATE user
76 <set>
77 <if test="username != null">
78 username = #{username,jdbcType=VARCHAR},
79 </if>
80 <if test="password != null">
81 password = #{password,jdbcType=VARCHAR},
82 </if>
83 <if test="age != null">
84 age = #{age,jdbcType=INTEGER},
85 </if>
86 <if test="createtime != null">
87 createtime = #{createtime,jdbcType=DATE},
88 </if>
89 </set>
90 WHERE id = #{id,jdbcType=BIGINT}
91 </update>
92 <update id="updateByPrimaryKey" parameterType="com.example.entity.User">
93 UPDATE user
94 SET username = #{username,jdbcType=VARCHAR},
95 password = #{password,jdbcType=VARCHAR},
96 age = #{age,jdbcType=INTEGER},
97 createtime = #{createtime,jdbcType=DATE},
98 WHERE id = #{id,jdbcType=BIGINT}
99 </update>
100 <delete id="deleteByPrimaryKey" parameterType="java.lang.Long">
101 DELETE FROM user
102 WHERE id = #{id,jdbcType=BIGINT}
103 </delete>
104
105 </mapper>
4. 服务和控制
1) 创建 src/main/java/com/example/service/UserService.java 文件
1 package com.example.service;
2
3 import com.example.entity.User;
4
5 public interface UserService {
6
7 int insert(User user);
8 User selectByPrimaryKey(Integer id);
9 User selectByUsername(String username);
10 int updateByPrimaryKey(User user);
11 int deleteByPrimaryKey(Integer id);
12 }
2) 创建 src/main/java/com/example/service/UserServiceImpl.java 文件
1 package com.example.service;
2
3 import org.springframework.beans.factory.annotation.Autowired;
4 import org.springframework.stereotype.Service;
5
6 import com.example.entity.User;
7 import com.example.mapper.UserMapper;
8
9 @Service("userService")
10 public class UserServiceImpl implements UserService {
11 @Autowired
12 UserMapper UserMapper;
13
14 @Override
15 public int insert(User user) {
16 return UserMapper.insert(user);
17 }
18
19 @Override
20 public User selectByPrimaryKey(Integer id) {
21 return UserMapper.selectByPrimaryKey(id);
22 }
23
24 @Override
25 public User selectByUsername(String username) {
26 return UserMapper.selectByUsername(username);
27 }
28
29 @Override
30 public int updateByPrimaryKey(User user) {
31 return UserMapper.updateByPrimaryKey(user);
32 }
33
34 @Override
35 public int deleteByPrimaryKey(Integer id) {
36 return UserMapper.deleteByPrimaryKey(id);
37 }
38
39 }
3) 创建 src/main/java/com/example/controller/UserController.java 文件
1 package com.example.controller;
2
3 import org.springframework.web.bind.annotation.RestController;
4 import org.springframework.web.bind.annotation.GetMapping;
5 import org.springframework.web.bind.annotation.PostMapping;
6 import org.springframework.beans.factory.annotation.Autowired;
7
8 import com.example.entity.User;
9 import com.example.service.UserService;
10
11 @RestController
12 public class UserController {
13 @Autowired
14 UserService UserService;
15
16 @GetMapping("/hello")
17 public String hello() {
18 return "hello";
19 }
20
21 }
注：如果不使用 JUnit 测试 UserService 的增删改查 (CRUD) 操作，我们需要在 UserController 里添加增删改查 (CRUD) 操作的方法，同时需要添加这些方法对应的 UI 代码 （HTML/CSS/Javascript）。
5. JUnit 测试用例
创建 test/java/com/example/service/UserServiceTest.java 文件
1 package com.example.service;
2
3 import static org.junit.Assert.*;
4
5 import java.util.Date;
6
7 import com.example.App;
8 import org.junit.Test;
9 import org.junit.runner.RunWith;
10 import org.junit.FixMethodOrder;
11 import org.junit.runners.MethodSorters;
12 import org.springframework.beans.factory.annotation.Autowired;
13 import org.springframework.boot.test.context.SpringBootTest;
14 import org.springframework.test.context.junit4.SpringRunner;
15
16 import com.example.entity.User;
17
18 @RunWith(SpringRunner.class)
19 @SpringBootTest(classes = App.class)
20 @FixMethodOrder(MethodSorters.NAME_ASCENDING) // DEFAULT：默认的顺序；JVM：按方法定义的顺序执行; NAME_ASCENDING：按方法名字母顺序执行；
21 public class UserServiceTest {
22 @Autowired
23 UserService userService;
24
25 @Test
26 public void unit01_addUser() {
27
28 User user = userService.selectByUsername("admin");
29 assertNull(user);
30
31 // Create
32 user = new User();
33 user.setUsername("admin");
34 user.setPassword("123456");
35 user.setAge(21);
36 user.setCreatetime(new Date());
37
38 int ret = userService.insert(user);
39 System.out.println("UserServiceTest -> unit01_addUser(): ret = " + ret);
40 assertTrue( ret > 0 );
41
42 }
43
44 @Test
45 public void unit02_selectUser() {
46
47 // Select
48 User user = userService.selectByUsername("admin");
49 assertTrue( 21 == user.getAge());
50 }
51
52 @Test
53 public void unit03_updateUser() {
54
55 // Update
56 User user = userService.selectByUsername("admin");
57 user.setAge(30);
58 int ret = userService.updateByPrimaryKey(user);
59 System.out.println("UserServiceTest -> unit03_updateUser(): ret = " + ret);
60 assertTrue( ret > 0 );
61
62 }
63
64 @Test
65 public void unit04_deleteUser() {
66
67 // Delete
68 User user = userService.selectByUsername("admin");
69 int ret = userService.deleteByPrimaryKey(user.getId());
70 System.out.println("UserServiceTest -> unit04_deleteUser(): ret = " + ret);
71 assertTrue( ret >= 0 );
72
73 }
74
75 }
注：设置 @FixMethodOrder(MethodSorters.NAME_ASCENDING) ，测试过程会依次执行如下方法：
unit01_addUser()
unit02_selectUser()
unit03_updateUser()
unit04_deleteUser()
运行测试用例：
Edit Configurations
Click "+" add new configuration -> Select "JUnit"
Name: UserServiceTest
Class: com.example.service.UserServiceTest
-> Apply / OK
Click Run "UserServiceTest"
...