關於Junit，官文甚至不做過多解釋：Junit只是一個用於單元測試的小框架，是基於xUnit架構的一個實現。

系列教程基於Maven。

1. 引入Junit依賴

<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope
 
>
    </dependency>
</dependencies>

貼士：Junit捆綁了一個hamcrest-core的類庫，檢視依賴樹可以看到：

dependency:tree
...
[INFO] \- junit:junit:jar:4.12:test
[INFO]    \- org.hamcrest:hamcrest-core:jar:1.3:test

如果你要使用hamcrest-core的其他版本，可以過濾掉hamcrest-core:

<dependencies>
        <dependency>
            <groupId
 
>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.hamcrest</groupId>
                    <artifactId
 
>hamcrest-core</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <!-- This will get hamcrest-core automatically 
        <dependency>
            <groupId>org.hamcrest</groupId>
            <artifactId>hamcrest-library</artifactId>
            <version>1.3</version>
            <scope>test</scope>
        </dependency>  -->
        <!-- https://mvnrepository.com/artifact/org.hamcrest/hamcrest-library -->
        <dependency>
            <groupId>org.hamcrest</groupId>
            <artifactId>hamcrest-library</artifactId>
        <version>1.4-atlassian-1</version>
    </dependency>

</dependencies>

2. Junit中的基本註解

Junit中集中基本註解，是必須掌握的。

• @BeforeClass – 表示在類中的任意public static void方法執行之前執行
• @AfterClass – 表示在類中的任意public static void方法執行之後執行
• @Before – 表示在任意使用@Test註解標註的public void方法執行之前執行
• @After – 表示在任意使用@Test註解標註的public void方法執行之後執行
• @Test – 使用該註解標註的public void方法會表示為一個測試方法

使用示例：
BasicAnnotationTest.java:

package org.byron4j.spring_mvc_log4j;

import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;

public class BasicAnnotationTest {
    // Run once, e.g. Database connection, connection pool
    @BeforeClass
    public static void runOnceBeforeClass() {
        System.out.println("@BeforeClass - runOnceBeforeClass");
    }

    // Run once, e.g close connection, cleanup
    @AfterClass
    public static void runOnceAfterClass() {
        System.out.println("@AfterClass - runOnceAfterClass");
    }

    // Should rename to @BeforeTestMethod
    // e.g. Creating an similar object and share for all @Test
    @Before
    public void runBeforeTestMethod() {
        System.out.println("@Before - runBeforeTestMethod");
    }

    // Should rename to @AfterTestMethod
    @After
    public void runAfterTestMethod() {
        System.out.println("@After - runAfterTestMethod");
    }

    @Test
    public void test_method_1() {
        System.out.println("@Test - test_method_1");
    }

    @Test
    public void test_method_2() {
        System.out.println("@Test - test_method_2");
    }
}

輸出：

@BeforeClass - runOnceBeforeClass
@Before - runBeforeTestMethod
@Test - test_method_1
@After - runAfterTestMethod
@Before - runBeforeTestMethod
@Test - test_method_2
@After - runAfterTestMethod
@AfterClass - runOnceAfterClass