java mock当前类的方法 java mock使用

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技术极客领袖 2023-08-19 22:37:02

文章标签 java mock当前类的方法单元测试数据库 java maven 文章分类 Java 后端开发

我们都编写了单元测试，但是有时我们面临的挑战是被测单元可能依赖于其他组件。并且配置其他组件进行单元测试绝对是一个过大的选择。相反，我们可以使用Mocks代替其他组件，并继续进行单元测试。

为了说明如何使用模拟，我有一个数据访问层（DAL），基本上是一个类，为应用程序提供API，以供应用程序访问和修改数据存储库中的数据。然后，我对DAL进行单元测试，而实际上无需连接到数据存储库。数据存储库可以是本地数据库或远程数据库，也可以是文件系统，也可以是我们可以存储和检索数据的任何位置。 DAL类的使用有助于我们将数据映射器与应用程序代码分开。

让我们使用maven创建一个Java项目。

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

上面创建了一个文件夹MockitoDemo，然后为源文件和测试文件创建了整个目录结构。

考虑此示例的以下模型类：

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;
  }
}

用于对Book模型类进行操作的DAL类为：

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;
  }
}

上面的DAL层目前没有功能，我们将对该单元代码（ TDD ）进行单元测试。 DAL层可能与我们在设计API时不关心的ORM映射器或数据库API通信。

测试DAL层

Java中有许多用于单元测试和模拟的框架，但是在这个示例中，我将选择JUnit用于单元测试，选择Mockito用于模拟。我们将不得不更新Maven的pom.xml中的依赖项

<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 http://maven.apache.org/maven-v4_0_0.xsd">
  <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>

现在让单元测试BookDAL 。在单元测试期间，我们会将模拟数据注入BookDAL中，以便我们无需依赖数据源即可完成API的测试。

最初，我们将有一个空的测试类：

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 {

  }
}

我们将把模拟的BookDAL和模拟的数据注入到setUp() ，如下所示：

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，我有：

BookDAL mockedBookDAL = mock(BookDAL.class);

//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());

填充其余的测试，我们得到：

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);
  }
}

可以使用maven命令运行测试： mvn test 。输出为：

-------------------------------------------------------
 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

因此，我们已经能够测试DAL类，而无需使用模拟实际配置数据源。

参考：来自Experiences Unlimited博客的JCG合作伙伴 Mohamed Sanaulla的Mockito 使用Java进行Mocking入门。

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