Java Mocking入门—使用Mockito，mockingmockito
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Java Mocking入门—使用Mockito，mockingmockito
我们都会编写单元测试程序，但我们当前所面临的挑战是被测单元可能依赖于其他组件。而对于单元测试配置其他组件，绝对是过枉矫正。相反，我们可以使用Mocks框架代替其他组件，继续进行单元测试。
为了展现如何使用mock框架，我编写一个数据访问层(DAL)，该类对应用提供了一套API 接口来访问和修改数据库中的数据。之后在不需要连接数据库的情况下，对DAL类进行单元测试。数据库可以是本地数据库、远程数据库、文件系统或者任何可以储存和检索数据的地方。使用DAL类帮助我们 将数据映射操作从应用代码中分离出来。
使用maven建立一个Java工程。
mvn archetype:generate -DgroupId=info.sanaulla -DartifactId=MockitoDemo -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false
以上操作建立了一个MockitoDemo文件夹，然后创建源文件和测试文件的整个目录结构。
考虑下面这个示例模型类：
package info.sanaulla.models;
import java.util.List;
/**
* Model class for the book details.
*/
public class Book {
private String isbn;
private String title;
private List<String> authors;
private String publication;
private Integer yearOfPublication;
private Integer numberOfPages;
private String image;
public Book(String isbn,
String title,
List<String> authors,
String publication,
Integer yearOfPublication,
Integer numberOfPages,
String image){
this.isbn = isbn;
this.title = title;
this.authors = authors;
this.publication = publication;
this.yearOfPublication = yearOfPublication;
this.numberOfPages = numberOfPages;
this.image = image;
}
public String getIsbn() {
return isbn;
}
public String getTitle() {
return title;
}
public List<String> getAuthors() {
return authors;
}
public String getPublication() {
return publication;
}
public Integer getYearOfPublication() {
return yearOfPublication;
}
public Integer getNumberOfPages() {
return numberOfPages;
}
public String getImage() {
return image;
}
}
操作Book模型类的DAL类：
package info.sanaulla.dal;
import info.sanaulla.models.Book;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
/**
* API layer for persisting and retrieving the Book objects.
*/
public class BookDAL {
private static BookDAL bookDAL = new BookDAL();
public List<Book> getAllBooks(){
return Collections.EMPTY_LIST;
}
public Book getBook(String isbn){
return null;
}
public String addBook(Book book){
return book.getIsbn();
}
public String updateBook(Book book){
return book.getIsbn();
}
public static BookDAL getInstance(){
return bookDAL;
}
}
当前DAL层以上没有任何功能，我们将对这段代码TDD进行单元测试。DAL层可能与ORM映射API或者数据库API通讯，而我们不关心的这些API是如何设计的。
测试驱动DAL层
对单元测试和Java Mock有很多框架，对这个例子，我将选择JUnit做单元测试，Mockito作为Java mock。我们会在Maven的pom.xml文件中更新依赖属性。
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 <a href="http://maven.apache.org/maven-v4_0_0.xsd">http://maven.apache.org/maven-v4_0_0.xsd"</a>>
<modelVersion>4.0.0</modelVersion>
<groupId>info.sanaulla</groupId>
<artifactId>MockitoDemo</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<name>MockitoDemo</name>
<url>http://maven.apache.org</url>
<dependencies>
<!-- Dependency for JUnit -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.10</version>
<scope>test</scope>
</dependency>
<!-- Dependency for Mockito -->
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-all</artifactId>
<version>1.9.5</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>
现在进行BookDAL类的单元测试。单元测试中，我们将注入mock数据到BookDAL类，因此我们可以不依赖数据源就可以完成API的测试。
最初我们有一个空的测试类:
public class BookDALTest {
public void setUp() throws Exception {
}
public void testGetAllBooks() throws Exception {
}
public void testGetBook() throws Exception {
}
public void testAddBook() throws Exception {
}
public void testUpdateBook() throws Exception {
}
}
我们将使用下面的setUp()函数把BookDAL类注入mock对象，并设置mock对象数据:
public class BookDALTest {
private static BookDAL mockedBookDAL;
private static Book book1;
private static Book book2;
@BeforeClass
public static void setUp(){
//Create mock object of BookDAL
mockedBookDAL = mock(BookDAL.class);
//Create few instances of Book class.
book1 = new Book("8131721019","Compilers Principles",
Arrays.asList("D. Jeffrey Ulman","Ravi Sethi", "Alfred V. Aho", "Monica S. Lam"),
"Pearson Education Singapore Pte Ltd", 2008,1009,"BOOK_IMAGE");
book2 = new Book("9788183331630","Let Us C 13th Edition",
Arrays.asList("Yashavant Kanetkar"),"BPB PUBLICATIONS", 2012,675,"BOOK_IMAGE");
//Stubbing the methods of mocked BookDAL with mocked data.
when(mockedBookDAL.getAllBooks()).thenReturn(Arrays.asList(book1, book2));
when(mockedBookDAL.getBook("8131721019")).thenReturn(book1);
when(mockedBookDAL.addBook(book1)).thenReturn(book1.getIsbn());
when(mockedBookDAL.updateBook(book1)).thenReturn(book1.getIsbn());
}
public void testGetAllBooks() throws Exception {}
public void testGetBook() throws Exception {}
public void testAddBook() throws Exception {}
public void testUpdateBook() throws Exception {}
}
在上面的setUp()方法中，我做了:
1. 创建一个BookDAL的mock对象
BookDAL mockedBookDAL = mock(BookDAL.class);
2. 存根带mock数据的BookDAL对象的API，这样无论何时调用API都可以返回mock数据。
//When getAllBooks() is invoked then return the given data and so on for the other methods.
when(mockedBookDAL.getAllBooks()).thenReturn(Arrays.asList(book1, book2));
when(mockedBookDAL.getBook("8131721019")).thenReturn(book1);
when(mockedBookDAL.addBook(book1)).thenReturn(book1.getIsbn());
when(mockedBookDAL.updateBook(book1)).thenReturn(book1.getIsbn());
填充剩余的测试方法:
package info.sanaulla.dal;
import info.sanaulla.models.Book;
import org.junit.BeforeClass;
import org.junit.Test;
import static org.junit.Assert.*;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;
import java.util.Arrays;
import java.util.List;
public class BookDALTest {
private static BookDAL mockedBookDAL;
private static Book book1;
private static Book book2;
@BeforeClass
public static void setUp(){
mockedBookDAL = mock(BookDAL.class);
book1 = new Book("8131721019","Compilers Principles",
Arrays.asList("D. Jeffrey Ulman","Ravi Sethi", "Alfred V. Aho", "Monica S. Lam"),
"Pearson Education Singapore Pte Ltd", 2008,1009,"BOOK_IMAGE");
book2 = new Book("9788183331630","Let Us C 13th Edition",
Arrays.asList("Yashavant Kanetkar"),"BPB PUBLICATIONS", 2012,675,"BOOK_IMAGE");
when(mockedBookDAL.getAllBooks()).thenReturn(Arrays.asList(book1, book2));
when(mockedBookDAL.getBook("8131721019")).thenReturn(book1);
when(mockedBookDAL.addBook(book1)).thenReturn(book1.getIsbn());
when(mockedBookDAL.updateBook(book1)).thenReturn(book1.getIsbn());
}
@Test
public void testGetAllBooks() throws Exception {
List<Book> allBooks = mockedBookDAL.getAllBooks();
assertEquals(2, allBooks.size());
Book myBook = allBooks.get(0);
assertEquals("8131721019", myBook.getIsbn());
assertEquals("Compilers Principles", myBook.getTitle());
assertEquals(4, myBook.getAuthors().size());
assertEquals((Integer)2008, myBook.getYearOfPublication());
assertEquals((Integer) 1009, myBook.getNumberOfPages());
assertEquals("Pearson Education Singapore Pte Ltd", myBook.getPublication());
assertEquals("BOOK_IMAGE", myBook.getImage());
}
@Test
public void testGetBook(){
String isbn = "8131721019";
Book myBook = mockedBookDAL.getBook(isbn);
assertNotNull(myBook);
assertEquals(isbn, myBook.getIsbn());
assertEquals("Compilers Principles", myBook.getTitle());
assertEquals(4, myBook.getAuthors().size());
assertEquals("Pearson Education Singapore Pte Ltd", myBook.getPublication());
assertEquals((Integer)2008, myBook.getYearOfPublication());
assertEquals((Integer)1009, myBook.getNumberOfPages());
}
@Test
public void testAddBook(){
String isbn = mockedBookDAL.addBook(book1);
assertNotNull(isbn);
assertEquals(book1.getIsbn(), isbn);
}
@Test
public void testUpdateBook(){
String isbn = mockedBookDAL.updateBook(book1);
assertNotNull(isbn);
assertEquals(book1.getIsbn(), isbn);
}
}
使用maven命令: mvn test进行测试。输出如下：
------------------------------------------------------- T E S T S ------------------------------------------------------- Running info.sanaulla.AppTest Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.029 sec Running info.sanaulla.dal.BookDALTest Tests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.209 sec Results : Tests run: 5, Failures: 0, Errors: 0, Skipped: 0
至此，通过使用mock框架，在不用实际配置数据源的情况下，就可以测试DAL类。
原文链接： dzone 翻译： Wld5.com - liken译文链接： http://www.wld5.com/10083.html
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