Mockito description method

The description method in the Mockito framework is used to add a custom description to be printed if a verification fails. This can help provide more context and clarity when a test does not pass, making it easier to understand what went wrong.

Table of Contents

1. Introduction
2. description Method Syntax
3. Examples
   • Basic Usage
   • Combining with Other Verification Modes
4. Real-World Use Case
5. Conclusion

Introduction

Mockito is a popular library in Java for creating and managing mock objects. The description method, which belongs to the Mockito class, allows you to specify a custom message that will be displayed if a verification fails. This can make debugging failing tests much easier by providing more informative error messages.

description Method Syntax

Adding a Description to Verification

import static org.mockito.Mockito.description;

static VerificationMode description(String description)

Adds a custom description to be printed if verification fails.

Parameters:

• description: The custom description message to be printed.

Returns:

• A VerificationMode object that can be used to add the description to the verification.

Examples

Basic Usage

Add a custom description to a verification.

import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.description;
import org.junit.jupiter.api.Test;

public class BasicDescriptionTest {
    @Test
    void testDescription() {
        UserService mockUserService = mock(UserService.class);

        // Perform some interactions
        mockUserService.deleteUser("123");

        // Verify with a custom description
        verify(mockUserService, description("User deletion verification failed")).deleteUser("123");
    }
}

class UserService {
    public void deleteUser(String userId) {
        // Method implementation
    }
}

Combining with Other Verification Modes

Combine a custom description with other verification modes.

import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.description;
import static org.mockito.Mockito.times;
import org.junit.jupiter.api.Test;

public class CombinedDescriptionTest {
    @Test
    void testCombinedDescription() {
        UserService mockUserService = mock(UserService.class);

        // Perform some interactions
        mockUserService.deleteUser("123");
        mockUserService.deleteUser("123");

        // Verify with a custom description and another verification mode
        verify(mockUserService, description("User deletion verification failed").times(2)).deleteUser("123");
    }
}

class UserService {
    public void deleteUser(String userId) {
        // Method implementation
    }
}

Real-World Use Case

Adding Context to Complex Verifications

In a real-world scenario, you might have complex verifications where adding a custom description can significantly help in understanding the cause of a failure.

import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.description;
import static org.mockito.Mockito.times;
import org.junit.jupiter.api.Test;

interface PaymentService {
    void processPayment(String orderId);
}

interface NotificationService {
    void sendNotification(String message);
}

class OrderService {
    private final PaymentService paymentService;
    private final NotificationService notificationService;

    public OrderService(PaymentService paymentService, NotificationService notificationService) {
        this.paymentService = paymentService;
        this.notificationService = notificationService;
    }

    public void placeOrder(String orderId) {
        paymentService.processPayment(orderId);
        notificationService.sendNotification("Order " + orderId + " placed");
    }

    public void processMultiplePayments(String orderId, int times) {
        for (int i = 0; i < times; i++) {
            paymentService.processPayment(orderId);
        }
    }
}

public class OrderServiceTest {
    @Test
    void testOrderServiceInteractionsWithDescription() {
        PaymentService mockPaymentService = mock(PaymentService.class);
        NotificationService mockNotificationService = mock(NotificationService.class);
        OrderService orderService = new OrderService(mockPaymentService, mockNotificationService);

        // Call methods on OrderService
        orderService.processMultiplePayments("123", 3);
        orderService.placeOrder("456");

        // Verify with a custom description
        verify(mockPaymentService, description("Payment processing verification failed").times(3)).processPayment("123");
        verify(mockNotificationService, description("Notification verification failed")).sendNotification("Order 456 placed");
    }
}

In this example, the OrderServiceTest class uses Mockito’s description method to add custom messages to the verifications. This helps ensure that if a verification fails, the error message will provide more context about what was expected, making it easier to diagnose the issue.

Conclusion

The description verification mode in Mockito is used for adding custom messages to verifications. By using description, you can provide more informative error messages when a verification fails, improving the clarity and debug-ability of your tests. This helps ensure that your tests are easier to understand and maintain.