原文地址:http://java.dzone.com/articles/getting-started-mocking-java文章通過一個簡單例項,介紹了使用Mockito建立mock物件來進行單元測試構建。例子淺顯易懂,相信希望瞭解mock的同學會有所收穫。文章的最後附上我實際構建的maven專案,大家有興趣可以自己實際操作下。

我們所有人在編寫單元測試的時候面臨的巨大挑戰是模組對其他元件的依賴。同時花費大量的時間和精力去配置依賴的元件環境是一件出力不討好的事情。使用Mock是一種有效地方式替代其他元件用來繼續我們的單元測試構建過程。

接下來我將會展示一個使用mock技術的例項。這裡我有一個數據訪問層(簡稱DAL),建立一個類,提供應用程式訪問和修改資料庫中資料的基本API。接著我會測試這個DAL例項,但並不真正連線資料庫。使用DAL類的目的是幫助我們隔離應用程式程式碼和資料顯示層。

讓我們通過下面的命令列建立一個java maven 專案。

mvn archetype:generate -DgroupId=info.sanaulla -DartifactId=MockitoDemo -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false

上述命令會建立一個名為MockitoDemo 的資料夾以及對應實體類的目錄結構和測試檔案。

請參考下面的例子來建立一個實體類:

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 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 getAuthors() {

return authors;

}

public String getPublication() {

return publication;

}

public Integer getYearOfPublication() {

return yearOfPublication;

}

public Integer getNumberOfPages() {

return numberOfPages;

}

public String getImage() {

return image;

}

}

用來操作Book類的DAL類如下:

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 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; } }

DAL 層現在並沒有實際的功能,我將嘗試用測試驅動開發的方式來構建(TDD)。我們並不關心,DAL層是通過實體關係對映來進行資料通訊還是通過其他資料庫API來實現上面的操作。

資料驅動的資料訪問層

有很多單元測試框架和mock框架,這裡我選擇Junit單元測試框架和moke框架Mockito。我們需要在pom.xml配置檔案中更新對他們的依賴。

   <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>

現在我們編寫BookDAL的單元測試類。通過單元測試,我們可以在BookDAL中注入mock物件進行單元測試而不用依賴其他資料來源。

首先建立一個空的測試類,程式碼如下:

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 {

} }

下面的程式碼中,我們在setUp方法中通過mock方式注入BookDAL物件

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setUp方法中我通過下面這種方式

1.建立BookDAL例項:

BookDAL mockedBookDAL = mock(BookDAL.class);

2.Mokito API中DAL的mock物件,使用when方法接收呼叫mock物件的方法返回值引數。

//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());

實現其他的已經宣告的測試方法：

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);

}

}



然後我們通過maven的命令航方式:mvn test運行當前的專案。控制檯輸出如下:

-——————————————————



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

現在我們就實現了即使不配置資料來源方式,而使用mock物件來測試DAL類。

例項程式碼