测试驱动开发

测试驱动开发，英文全称Test-Driven Development，简称TDD，是一种不同于传统软件开发流程的新型的开发方法。它要求在编写某个功能的代码之前先编写测试代码，然后只编写使测试通过的功能代码，通过测试来推动整个开发的进行。这有助于编写简洁可用和高质量的代码，并加速开发过程。

传统的的开发流程：
编码--->测试--->重复--->提交

基于测试驱动的开发流程：
测试--->编码--->重复--->提交

下面是一个简单的用户管理的用测试驱动开发的小小例子：

1、先定义好实体类User：

package com.fjnu.model;

public class User {
	private String username;
	private String password;
	private String nickname;
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	public String getNickname() {
		return nickname;
	}
	public void setNickname(String nickname) {
		this.nickname = nickname;
	}
	public User() {
		super();
		// TODO Auto-generated constructor stub
	}
	public User(String username, String password, String nickname) {
		super();
		this.username = username;
		this.password = password;
		this.nickname = nickname;
	}
	
}

2、然后定义好数据操作层的接口IUserService：

package com.fjnu.service;

import com.fjnu.model.User;

public interface IUserService {
	public void add(User user);
	
	public void delete(String username);
	
	public User load(String username);
	
	public User login(String username, String password);
}

3、再定义一个异常类UserException，继承RuntimeException。

4、有了这些，就可以针对接口IUserService编写测试类TestUserService了，这个测试类类似于白盒测试，要把各种分支的可能情况都要考虑到并且编写测试代码：

package com.fjnu.service;

import static org.junit.Assert.*;

import org.junit.Before;
import org.junit.Test;

import com.fjnu.model.User;
import com.fjnu.model.UserException;


public class TestUserService {
	private IUserService us;
	private User baseUser;
	
	@Before
	public void setUp(){
		// 初始化
		us = new UserServiceByMap();
		baseUser = new User("admin", "123", "管理员");
	}
	
	private void assertUserEquals(User u, User tu){
		assertEquals("add方法有错误!", u.getUsername(), tu.getUsername());
		assertEquals("add方法有错误!", u.getNickname(), tu.getNickname());
		assertEquals("add方法有错误!", u.getPassword(), tu.getPassword());
	}
	
	@Test
	public void testAdd(){
		User u = baseUser;
		us.add(u);
		User tu = us.load("admin");
		assertNotNull(tu);
		assertUserEquals(u, tu);
		//fail("请加入添加的测试代码");
	}
	
	@Test(expected=UserException.class)
	public void AddExistUsername(){
		us.add(baseUser);
		User tu = new User("admin", "1234", "alskdf");
		us.add(tu);
	}
	
	@Test
	public void testDelete(){
		us.add(baseUser);
		User tu = us.load(baseUser.getUsername());
		assertNotNull(tu);
		us.delete(baseUser.getUsername());
		tu = us.load(baseUser.getUsername());
		assertNull(tu);
	}
	
	@Test
	public void testLogin(){
 		us.add(baseUser);
		String username=baseUser.getUsername();
		String password=baseUser.getPassword();
		User tu = us.login(username, password);
		assertUserEquals(baseUser, tu);
	}
	
	@Test(expected=UserException.class)
	public void testNotExistsUserLogin(){
		us.add(baseUser);
		String username="admin1";
		String password="123";
		us.login(username, password);
 	}
	
	@Test(expected=UserException.class)
	public void testPasswordErrorUserLogin(){
		us.add(baseUser);
		String username="admin";
		String password="1235";
		us.login(username, password);
	}
}

5、编写完测试类之后，就可以实现接口IUserService了：

package com.fjnu.service;

import java.util.HashMap;
import java.util.Map;

import com.fjnu.model.User;
import com.fjnu.model.UserException;

public class UserServiceByMap implements IUserService {
	private Map<String, User> us = new HashMap<String, User>();
	
	@Override
	public void add(User user) {
		// TODO Auto-generated method stub
		if(load(user.getUsername()) != null){
			throw new UserException("用户名已存在");
		}
		us.put(user.getUsername(), user);
	}

	@Override
	public void delete(String username) {
		// TODO Auto-generated method stub
		us.remove(username);
	}

	@Override
	public User load(String username) {
		// TODO Auto-generated method stub
		return us.get(username);
	}

	@Override
	public User login(String username, String password) {
		// TODO Auto-generated method stub
		User u = load(username);
		if(u==null) throw new UserException("用户名不存在");
		if(!u.getPassword().equals(password)) throw new UserException("用户密码不正确");
		return u;
	}

}

最终：