JUnit + Spring integration example

In this tutorial, we will show you how to test the Spring DI components with JUnit frameworks.

Technologies used :

1. JUnit 4.12
2. Hamcrest 1.3
3. Spring 4.3.0.RELEASE
4. Maven

1. Project Dependencies

To integrate Spring with JUnit, you need spring-test.jar

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.hamcrest</groupId>
                    <artifactId>hamcrest-core</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.hamcrest</groupId>
            <artifactId>hamcrest-library</artifactId>
            <version>1.3</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.0.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>4.3.0.RELEASE</version>
            <scope>test</scope>
        </dependency>

2. Spring Components

A simple Spring components, later for testing.

2.1 An interface.

package com.mkyong.examples.spring;
public interface DataModelService {
    boolean isValid(String input);

2.2 Implementation of above interface.

package com.mkyong.examples.spring;
import org.springframework.stereotype.Service;
@Service("ml")
public class MachineLearningService implements DataModelService {
    @Override
    public boolean isValid(String input) {
        return true;

2.2 A Spring configuration file, component scanning.

package com.mkyong.examples.spring;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
@ComponentScan(basePackages = {"com.mkyong.examples.spring"})
public class AppConfig {

3. JUnit + Spring Integration Examples

Annotate the JUnit test class with @RunWith(SpringJUnit4ClassRunner.class) and loads the Spring configuration file manually. Refer below :

package com.mkyong.spring;
import com.mkyong.examples.spring.AppConfig;
import com.mkyong.examples.spring.DataModelService;
import com.mkyong.examples.spring.MachineLearningService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.instanceOf;
import static org.hamcrest.Matchers.is;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = {AppConfig.class})
public class MachineLearningTest {
	//DI
    @Autowired
    @Qualifier("ml")
    DataModelService ml;
    @Test
    public void test_ml_always_return_true() {
        //assert correct type/impl
        assertThat(ml, instanceOf(MachineLearningService.class));
        //assert true
        assertThat(ml.isValid(""), is(true));

Done.

4. FAQs

4.1 For XML, try this :

import org.springframework.test.context.ContextConfiguration;
@ContextConfiguration(locations = {
        "classpath:pathTo/appConfig.xml",
        "classpath:pathTo/appConfig2.xml"})
public class MachineLearningTest {
//...

4.2 For multiple configuration files :

import org.springframework.test.context.ContextConfiguration;
@ContextConfiguration(classes = {AppConfig.class, AppConfig2.class})
public class MachineLearningTest {
//...

References

1. Spring IO – Unit Testing
2. Spring IO – Integration Testing
3. TestNG + Spring Integration Example
4. Spring Batch unit test example