Java learning route (22) - testing framework Junit

1. The concept of unit testing
Unit testing is to write test code for the smallest functional unit. The smallest functional unit of a Java program is a method. Therefore, unit testing is a test for a Java method, and then checks the correctness of the method.

Two, Junit test framework

(1) Concept: Junit is a unit testing framework implemented in the Java language.
(2) Advantages:

• Optional test method
• Execute all test methods with one click
• Junit can generate test reports for all methods
• The test method is isolated
  (3) to achieve unit testing
• 1. Import the JUnit package, which is not required if the IDE has integrated the Junit framework.
  
• 2. Write a test method: the method must be a public non-static method with no parameters and no counters
• 3. Add @Test annotation
• 4. The test method completes the expected correctness test.
• 5. Run the test method. (Green - passed, red - failed)

Business code

public class UserService {
    
    
    public String login(String loginname,String password){
    
    
        if ("admin2".equals(loginname) && "123456".equals(password)) return "登录成功";
        else return "用户名或密码错误";
    }

    public void selectName(){
    
    
        System.out.println(10 / 0);
        System.out.println("查询全部用户名");
    }
}

test code

public class TestDemo{
    
    
    @Test
    public void testLogin(){
    
    
        UserService service = new UserService();
        String rs = service.login("admin","123456");

        //预期结果的测试Assert——断言测试
        Assert.assertEquals("功能业务出错!!","登录成功",rs);
    }

    @Test
    public void testSelectName(){
    
    
        UserService service = new UserService();
        service.selectName();
    }
}

Effect output 1

org.junit.ComparisonFailure: 功能业务出错!! 
Expected :登录成功
Actual   :用户名或密码错误
<Click to see difference>
	at org.junit.Assert.assertEquals(Assert.java:117)
	at com.zengoo.junit.TestDemo.testLogin(TestDemo.java:18)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
	at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)

One-key test

Effect diagram

(4) Junit common annotations (Junit 4.0 and above)

annotation	illustrate
@Test	Test Methods
@Before	Modified instance method, executed before each test method is executed
@After	Modified instance method, executed after each test method is executed
@BeforeClass	Static decoration method, executed only once before all test methods are executed
@AfterClass	Static decoration method, executed only once after all test methods are executed