Test unitaire - Qu’est-ce que se moquer? et pourquoi?

Test unitaire - Qu'est-ce que la moquerie? et pourquoi?

En termes simples, se moquer consiste à créer des objets qui imitent le comportement d'objets réels. Reportez-vous à l'étude de cas suivante:

Testé:

Java 1.8
JUnit 4.12
Mockito 2.0.73-bêta

Mock Object
Lisez ceciWikipedia Mock object.

1. Exemples Java

Un exemple simple d'auteur et de livre.

1.1 BookService to return a list of books by author name.

BookService.java

package com.example.examples.mock;

import java.util.List;

public interface BookService {

    List findBookByAuthor(String author);

}

BookServiceImpl.java

package com.example.examples.mock;

import java.util.List;

public class BookServiceImpl implements BookService {

    private BookDao bookDao;

    public BookDao getBookDao() {
        return bookDao;
    }

    public void setBookDao(BookDao bookDao) {
        this.bookDao = bookDao;
    }

    @Override
    public List findBookByAuthor(String name) {
        return bookDao.findBookByAuthor(name);
    }

}

BookDao.java

package com.example.examples.mock;

import java.util.List;

public interface BookDao {

    List findBookByAuthor(String author);

}

BookDaoImpl.java

package com.example.examples.mock;

import java.util.List;

public class BookDaoImpl implements BookDao {

    @Override
    public List findBookByAuthor(String name) {
        // init database
        // Connect to DB for data
        // return data
    }

}

1.2 A book validator.

BookValidatorService.java

package com.example.examples.mock;

public interface BookValidatorService {

    boolean isValid(Book book);

}

FakeBookValidatorService.java

package com.example.examples.mock;

public class FakeBookValidatorService implements BookValidatorService {

    @Override
    public boolean isValid(Book book) {
        if (book == null)
            return false;

        if ("bot".equals(book.getName())) {
            return false;
        } else {
            return true;
        }

    }
}

1.3 Reviews the AuthorServiceImpl, it has dependencies on BookService (depends on BookDao) and BookValidatorService, it makes the unit test a bit hard to write.

AuthorService.java

package com.example.examples.mock;

public interface AuthorService {

    int getTotalBooks(String author);

}

AuthorServiceImpl.java

package com.example.examples.mock;

import java.util.List;
import java.util.stream.Collectors;

public class AuthorServiceImpl implements AuthorService {

    private BookService bookService;
    private BookValidatorService bookValidatorService;

    public BookValidatorService getBookValidatorService() {
        return bookValidatorService;
    }

    public void setBookValidatorService(BookValidatorService bookValidatorService) {
        this.bookValidatorService = bookValidatorService;
    }

    public BookService getBookService() {
        return bookService;
    }

    public void setBookService(BookService bookService) {
        this.bookService = bookService;
    }

    //How to test this method ???
    @Override
    public int getTotalBooks(String author) {

        List books = bookService.findBookByAuthor(author);

        //filters some bot writers
        List filtered = books.stream().filter(
                x -> bookValidatorService.isValid(x))
                .collect(Collectors.toList());

        //other business logic

        return filtered.size();


    }
}

2. Test de l'unité

Créer un test unitaire pourAuthorServiceImpl.getTotalBooks()

2.1 The AuthorServiceImpl has two dependencies, you need to make sure both are configured properly.

AuthorServiceTest.java

package com.example.mock;

import com.example.examples.mock.AuthorServiceImpl;
import com.example.examples.mock.BookDaoImpl;
import com.example.examples.mock.BookServiceImpl;
import com.example.examples.mock.FakeBookValidatorService;
import org.junit.Test;

import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertThat;

public class AuthorServiceTest {

    @Test
    public void test_total_book_by_mock() {

        //1. Setup
        AuthorServiceImpl obj = new AuthorServiceImpl();
        BookServiceImpl bookService = new BookServiceImpl();
        bookService.setBookDao(new BookDaoImpl()); //Where Dao connect to?
        obj.setBookService(bookService);
        obj.setBookValidatorService(new FakeBookValidatorService());

        //2. Test method
        int qty = obj.getTotalBooks("example");

        //3. Verify result
        assertThat(qty, is(2));

    }

}

Pour réussir le test unitaire ci-dessus, vous devez configurer une base de données dans la couche DAO, sinonbookService ne retournera rien.

2.3 Some disadvantages to perform tests like above :

Ce test unitaire est lent, car vous devez démarrer une base de données pour obtenir des données de DAO.
Ce test unitaire n'est pas isolé, il dépend toujours de ressources externes comme la base de données.
Ce test unitaire ne peut pas garantir que la condition de test est toujours la même, les données de la base de données peuvent varier dans le temps.
Tester une méthode simple représente trop de travail, car les développeurs sautent le test.

2.4 Solution
The solution is obvious, you need a modified version of the BookServiceImpl class – which will always return the same data for testing, a mock object!

What is mocking?
Encore une fois, se moquer consiste à créer des objets qui imitent le comportement d'objets réels.

3. Test unitaire - Objet simulé

3.1 Create a new MockBookServiceImpl class and always return the same collection of books for author “example”.

MockBookServiceImpl.java

package com.example.mock;

import com.example.examples.mock.Book;
import com.example.examples.mock.BookService;

import java.util.ArrayList;
import java.util.List;

//I am a mock object!
public class MockBookServiceImpl implements BookService {

    @Override
    public List findBookByAuthor(String author) {
        List books = new ArrayList<>();

        if ("example".equals(author)) {
            books.add(new Book("example in action"));
            books.add(new Book("abc in action"));
            books.add(new Book("bot"));
        }

        return books;
    }

    //implements other methods...

}

3.2 Update the unit test again.

AuthorServiceTest.java

package com.example.mock;

import com.example.examples.mock.AuthorServiceImpl;
import com.example.examples.mock.FakeBookValidatorService;
import org.junit.Test;

import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertThat;

public class AuthorServiceTest {

    @Test
    public void test_total_book_by_mock() {

        //1. Setup
        AuthorServiceImpl obj = new AuthorServiceImpl();

        /*BookServiceImpl bookService = new BookServiceImpl();
        bookService.setBookDao(new BookDaoImpl());
        obj.setBookService(bookService);*/

        obj.setBookService(new MockBookServiceImpl());
        obj.setBookValidatorService(new FakeBookValidatorService());

        //2. Test method
        int qty = obj.getTotalBooks("example");

        //3. Verify result
        assertThat(qty, is(2));

    }

}

Le test unitaire ci-dessus est bien meilleur, rapide, isolé (plus de base de données) et la condition de test (données) est toujours la même.

3.3 But, there are some disadvantages to create mock object manually like above :

À la fin, vous pouvez créer de nombreux objets (classes) fictifs, juste à des fins de test unitaire.
Si l'interface contient de nombreuses méthodes, vous devez remplacer chacune d'elles.
C’est encore trop de travail et compliqué!

3.4 Solution
Try Mockito, a simple and powerful mocking framework.

4. Test unitaire - Mockito

4.1 Update the unit test again, this time, create the mock object via Mockito framework.

pom.xml

    
            org.mockito
            mockito-core
            2.0.73-beta

AuthorServiceTest.java

package com.example.mock;

import com.example.examples.mock.AuthorServiceImpl;
import com.example.examples.mock.Book;
import com.example.examples.mock.BookServiceImpl;
import com.example.examples.mock.FakeBookValidatorService;
import org.junit.Test;

import java.util.Arrays;
import java.util.List;

import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertThat;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

public class AuthorServiceTest {

        @Test
        public void test_total_book_by_mockito() {

            //1. Setup
            List books = Arrays.asList(
                    new Book("example in action"),
                    new Book("abc in action"),
                    new Book("bot"));

            BookServiceImpl mockito = mock(BookServiceImpl.class);

            //if the author is "example", then return a 'books' object.
            when(mockito.findBookByAuthor("example")).thenReturn(books);

            AuthorServiceImpl obj = new AuthorServiceImpl();
            obj.setBookService(mockito);
            obj.setBookValidatorService(new FakeBookValidatorService());

            //2. Test method
            int qty = obj.getTotalBooks("example");

            //3. Verify result
            assertThat(qty, is(2));

        }

}

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TOC

Test unitaire - Qu’est-ce que se moquer? et pourquoi?

Test unitaire - Qu'est-ce que la moquerie? et pourquoi?

1. Exemples Java

2. Test de l'unité

3. Test unitaire - Objet simulé

4. Test unitaire - Mockito

Références

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