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。
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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：
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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：
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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。
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<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:
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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:
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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
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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。
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//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:
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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：
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------------------------------------------------------- T E S T S-------------------------------------------------------Running info.sanaulla.AppTestTests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.029 secRunning info.sanaulla.dal.BookDALTestTests run: 4, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.209 secResults :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： ImportNew.com - liken译文链接： http://www.importnew.com/10083.html
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