Enterprise Java

SpringRunner vs. SpringBootTest

Testing is essential for all applications, encompassing both unit and integration tests. The cornerstone for conducting integration tests lies in classes like SpringRunner and SpringBootTest. Let’s explore SpringRunner vs. SpringBootTest.

1. Exploring SpringRunner in Spring Testing

SpringRunner is a test runner provided by the Spring framework for running JUnit tests with Spring support. It plays a crucial role in integrating JUnit tests with the Spring TestContext Framework, enabling features such as dependency injection and transaction management during testing.

When writing unit tests or integration tests for Spring applications, you often need to load the Spring application context and perform tests within the context of the Spring environment. SpringRunner facilitates this process by integrating JUnit with Spring’s testing support.

To use SpringRunner, you annotate your test class with @RunWith(SpringRunner.class). This annotation tells JUnit to use SpringRunner as the test runner. Additionally, you can use other annotations like @SpringBootTest to specify which Spring context to load for the test.

With SpringRunner, you can leverage the full power of Spring’s dependency injection and configuration management during testing, making it easier to write comprehensive tests for your Spring-based applications. One of the primary benefits of using SpringRunner is its ability to provide a Spring-aware testing environment. This means that your tests can access Spring beans and configurations, allowing you to write tests that closely resemble the behavior of your application in a real-world scenario.

2. Understanding SpringBootTest Annotation

SpringBootTest is a class provided by the Spring Framework for writing integration tests for Spring applications. Here are some key features of this annotation:

  • Annotation-driven Testing: Spring Boot Test provides a set of annotations such as @SpringBootTest, @WebMvcTest, @DataJpaTest, etc., which allow developers to easily configure and customize their tests based on the requirements of the application components being tested.
  • Integration Testing Support: Spring Boot Test enables integration testing by automatically configuring and starting an embedded application context for testing. This allows developers to test the entire Spring application context, including controllers, services, repositories, and other components, like how it would run in a production environment.
  • Auto-configuration: Spring Boot Test leverages Spring Boot’s auto-configuration capabilities to automatically configure the application context for testing. This reduces the need for explicit configuration in test classes, resulting in cleaner and more concise test code.
  • Embedded Server Support: For testing web applications, Spring Boot Test provides support for embedded servers such as Tomcat, Jetty, and Undertow. This allows developers to test their web endpoints without needing to deploy the application to an external server.
  • Test Slices: Spring Boot Test offers test slice annotations like @WebMvcTest, @DataJpaTest, and @RestClientTest, which allow developers to create focused tests that only load the relevant parts of the application context. This improves test performance and encourages writing more isolated and targeted tests.
  • Environment Customization: With Spring Boot Test, developers can easily customize the test environment by providing properties in the application.properties file or through annotations like @TestPropertySource. This flexibility enables testing under different configurations and scenarios.
  • Test Lifecycle Management: Spring Boot Test provides hooks for managing the test lifecycle, allowing developers to perform setup and teardown operations before and after tests are run. This ensures that tests are executed in a predictable and controlled environment.
  • Spring Boot Test Utilities: Spring Boot Test offers utilities like TestRestTemplate, MockMvc, and TestEntityManager for writing expressive and powerful tests. These utilities provide convenient methods for interacting with REST endpoints, performing HTTP requests, and interacting with databases during testing.

2.1 Usage

To use SpringBootTest, annotate your test class with @SpringBootTest. This annotation loads the complete Spring application context.

import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.junit.runner.RunWith;

public class MySpringBootTest {
  // Test methods go here

2.2 Code Example

Below is an example of using SpringBootTest to test a controller in a Spring Boot application.

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.web.client.TestRestTemplate;
import org.springframework.boot.web.server.LocalServerPort;
import org.springframework.http.ResponseEntity;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class MyControllerTest {

  private int port;

  private TestRestTemplate restTemplate;

  private String baseUrl;

  public void setUp() {
    this.baseUrl = "http://localhost:" + port + "/api";

  public void testGet() {
    ResponseEntity<String> responseEntity = restTemplate.getForEntity(baseUrl + "/endpoint", String.class);
    assertEquals(200, responseEntity.getStatusCodeValue());
    assertEquals("ExpectedResponse", responseEntity.getBody());

3. Comparison Between SpringRunner and SpringBootTest

When it comes to testing Spring applications, both SpringRunner and SpringBootTest play significant roles, but they serve different purposes and are used in different contexts. Let’s explore their differences:

Primary UseUnit testing with Spring supportIntegration testing of Spring Boot applications
PurposeInitializes Spring application context for unit testsConfigures and starts embedded application context for integration tests
ScopeFocuses on testing individual components or units in isolationTests the entire application context, including controllers, services, repositories, etc.
Dependency InjectionSupports dependency injection of Spring beans into test classesAutomatically wires Spring beans and configurations into the test context
Transaction ManagementProvides transaction management for unit testsHandles transactions for integration tests using embedded database
FlexibilityOffers more control over the testing environmentOffers convenience and ease of testing with minimal setup

4. Conclusion

In conclusion, by leveraging both SpringRunner and SpringBootTest effectively, developers can create a robust testing strategy that covers both unit and integration testing aspects, ultimately leading to the development of high-quality and reliable Spring applications.

Yatin Batra

An experience full-stack engineer well versed with Core Java, Spring/Springboot, MVC, Security, AOP, Frontend (Angular & React), and cloud technologies (such as AWS, GCP, Jenkins, Docker, K8).
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