一、概念
junit是一个专门测试的框架
集合maven进行单元测试，可批量测试类中的大量方法是否符合预期
二、作用：
单元测试：测试的内容是类中的方法，每一个方法都是独立测试的。方法是测试的基本单位。
三、使用方法
1、pom内加入依赖
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
2、在maven中src/test/java目录下的，创建测试程序。
推荐的创建类和方法的提示：
1、测试类的名称：Test+待测试类名
2、测试方法的名称：Test+方法名称
例如：你要测试HelloMaven
创建测试类TestHelloMaven
@Test
public void testaDD(){
测试HelloMaven的add方法是否正确
}
其中testAdd叫做测试方法，定义规则：
1、方法必须是public的
2、方法必须没有返回值
3、方法名称自定义，推荐是Test+被测方法
4、方法上面加上注解@Test
四、举例，Hello项目
1、新建java源程序，存放在Hellosrcmainjavacom estbk目录下，取名HelloMaven.java
package com.testbk;
import org.junit.Assert;
import org.junit.Test;
public class TestHelloMaven{
@Test
public void testAdd(){
System.out.println("maven junit testAdd()===")
HelloMaven hello = new HelloMaven();
int res = hello.add(10,20);
//验证10+20是不是30，juit提供的方法，对比结果的
//assertEquals(期望值，实际值)
Assert.assertEquals(30,res)
}
}
2、新建maven测试类型，存放在Hellosrcmainjavacom estbk目录下，取名TestHelloMaven.java
package com.testbk;
import org.junit.Assert;
import org.junit.Test;
public class TestHelloMaven{
@Test
public void testAdd(){
System.out.println("maven junit testAdd()===")
HelloMaven hello = new HelloMaven();
int res = hello.add(10,20);
//验证10+20是不是30，juit提供的方法，对比结果的
//assertEquals(期望值，实际值)
Assert.assertEquals(30,res)
}
@Test
public void testAdd2(){
System.out.println("#####maven junit testAdd()2###");
HelloMaven hello = new HelloMaven();
int res = hello.add(10,20);
//验证10+20是不是30，juit提供的方法，对比结果的
//assertEquals(期望值，实际值)
Assert.assertEquals(50,res);
}
}
3、执行mvn clean：清理target目录
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------< com.testbk:testjava >-------------------------
[INFO] Building maven 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ testjava ---
[INFO] Deleting D:javaProjectsHello arget
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.196 s
[INFO] Finished at: 2021-04-25T22:50:10+08:00
[INFO] ------------------------------------------------------------------------
4、执行mvn compile：编译main/java目录下的java为class文件，同时把class拷贝到target/classes目录下面
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------< com.testbk:testjava >-------------------------
[INFO] Building maven 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ testjava ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 0 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ testjava ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to D:javaProjectsHello argetclasses
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.724 s
[INFO] Finished at: 2021-04-25T22:54:23+08:00
[INFO] ------------------------------------------------------------------------
5、执行mvn test-compile:编译test/java目录下的java为class文件，同时class拷贝到target/test-classes目录下面
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------< com.testbk:testjava >-------------------------
[INFO] Building maven 0.0.1-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ testjava ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 0 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ testjava ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ testjava ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Copying 0 resource
[INFO]
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ testjava ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to D:javaProjectsHello arget est-classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.764 s
[INFO] Finished at: 2021-04-25T22:55:43+08:00
[INFO] ------------------------------------------------------------------------
6、执行mvn test：查看测试结果，通过1，失败1，并在指定目录生成测试报告
Results :
Failed tests: testAdd2(com.testbk.TestHelloMaven): expected:<50> but was:<30>
Tests run: 2, Failures: 1, Errors: 0, Skipped: 0
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.050 s
[INFO] Finished at: 2021-04-25T22:57:16+08:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.12.4:test (default-test) on project testjava: There are test failures.
[ERROR]
[ERROR] Please refer to D:javaProjectsHello argetsurefire-reports for the individual test results.
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException
7、修改测试代码，并再次执行mvn test
package com.testbk;
import org.junit.Assert;
import org.junit.Test;
public class TestHelloMaven{
@Test
public void testAdd(){
System.out.println("=====maven junit testAdd()===");
HelloMaven hello = new HelloMaven();
int res = hello.add(10,20);
//验证10+20是不是30，juit提供的方法，对比结果的
//assertEquals(期望值，实际值)
Assert.assertEquals(30,res);
}
@Test
public void testAdd2(){
System.out.println("#####maven junit testAdd()2###");
HelloMaven hello = new HelloMaven();
int res = hello.add(30,20);
//验证10+20是不是30，juit提供的方法，对比结果的
//assertEquals(期望值，实际值)
Assert.assertEquals(50,res);
}
}
查看运行结果，测试通过
T E S T S
-------------------------------------------------------
Running com.testbk.TestHelloMaven
=====maven junit testAdd()===
#####maven junit testAdd()2###
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.034 sec
Results :
Tests run: 2, Failures: 0, Errors: 0, Skipped: 0
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.282 s
[INFO] Finished at: 2021-04-25T22:58:41+08:00
[INFO] ------------------------------------------------------------------------