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  • Java Mocking入门—使用Mockito

    Java Mocking入门—使用Mockito

    2014/03/10 | 分类： 基础技术 | 0 条评论 | 标签： 单元测试

    分享到：8
    本文由 ImportNew - liken 翻译自 dzone。欢迎加入翻译小组。转载请见文末要求。

    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.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： ImportNew.com - liken
    译文链接： http://www.importnew.com/10083.html
    [ 转载请保留原文出处、译者和译文链接。]
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  • 原文地址：https://www.cnblogs.com/developer-ios/p/5382052.html
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