spring boot test junit null pointer exception

Question

im new on this of unit tests, so im trying to code the unit test for my service, right now i have this class

package com.praxis.topics.service;
import com.praxis.topics.exception.EntityNotFoundException;
import com.praxis.topics.model.Topic;
import com.praxis.topics.model.enums.Status;
import com.praxis.topics.repository.TopicRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.time.LocalDateTime;
import java.util.List;

@Service("topics")
public class TopicServiceImpl implements TopicService {
   private final TopicRepository topicRepository;

   @Autowired
   public TopicServiceImpl(TopicRepository topicRepository) {
       this.topicRepository = topicRepository;
   }

   @Override
   public List<Topic> getTopicsByStatus(int status) {
       // Check if status exists in enum
       if (status < 0 || Status.values().length - 1 < status)
           throw new ArrayIndexOutOfBoundsException(status);

       return topicRepository.findTopicByStatus(Status.values()[status]);
   }

   @Override
   public Topic addTopic(Topic topic) {

       //topic.setCreatedAt(LocalDateTime.now());
       return topicRepository.save(topic);
   }

   @Override
   public Topic updateTopic(Topic topic) throws EntityNotFoundException {
       if (topicRepository.findTopicById(topic.getId()) == null)
           throw new EntityNotFoundException(String.format("Topic with    id:             %s was not found", topic.getId()));

           return topicRepository.save(topic);
   }

   @Override
   public Topic getTopicById(String id) {
       return topicRepository.findTopicById(id);
   }

   @Override
   public void deleteTopicById(String id) {
      topicRepository.deleteTopicById(id);
   }

   @Override
   public List<Topic> getTopicsByName(String name) {
      return topicRepository.findAllByNameContains(name);
   }

   @Override
   public Topic getTopicByName(String name) {
      return topicRepository.findTopicByName(name);
   }

   @Override
   public List<Topic>getAllTopics(){
      return topicRepository.findAll();
   }

}

the model of topics is this

package com.praxis.topics.model;
import com.praxis.topics.model.enums.Status;
import org.hibernate.validator.constraints.NotEmpty; 
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;
import org.springframework.format.annotation.DateTimeFormat;
import java.time.LocalDateTime;

@Document(collection = "Topic")
public class Topic {
    @Id
    private String id;

    @NotEmpty(message = "The name is required")
    private String name;

    @NotEmpty(message = "The description is required")
    private String description;

    private Status status;
    private String chat;
    private int teachers;
    private int students;

    @DateTimeFormat(pattern = "dd-MM-yyyy hh:mm:ss")
    private LocalDateTime createdAt;

    @DateTimeFormat(pattern = "dd-MM-yyyy hh:mm:ss")
    private LocalDateTime openedAt;

    @DateTimeFormat(pattern = "dd-MM-yyyy hh:mm:ss")
    private LocalDateTime closedAt;

    public Topic() {}

    public Topic(String name, String description) {
        this.name = name;
        this.description = description;
        this.createdAt = LocalDateTime.now();
    }

and im trying to do this test for but it throws me a null pointer exception, like if the service variable wasnt initialized or something

package com.praxis.topics.service; 
import com.praxis.topics.model.Topic;
import com.praxis.topics.repository.TopicRepository;
import org.springframework.beans.factory.annotation.Autowired;
import static org.junit.jupiter.api.Assertions.*;

class TopicServiceImplTest {

   @Autowired
   TopicServiceImpl service;

   @org.junit.jupiter.api.Test
   void addTopic() {
       Topic topic = new Topic("java", "test");
       assertEquals(topic, service.addTopic(topic));
   }
}

and this are the exceptions i get

java.lang.NullPointerException at   com.praxis.topics.service.TopicServiceImplTest.addTopic(TopicServiceImplTest.java:29)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:436)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:115)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:170)
at org.junit.jupiter.engine.execution.ThrowableCollector.execute(ThrowableCollector.java:40)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:166)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:113)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:58)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$NodeExecutor.lambda$executeRecursively$3(HierarchicalTestExecutor.java:112)
at org.junit.platform.engine.support.hierarchical.SingleTestExecutor.executeSafely(SingleTestExecutor.java:66)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$NodeExecutor.executeRecursively(HierarchicalTestExecutor.java:108)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$NodeExecutor.execute(HierarchicalTestExecutor.java:79)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$NodeExecutor.lambda$executeRecursively$2(HierarchicalTestExecutor.java:120)
at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:177)
at java.base/java.util.Iterator.forEachRemaining(Iterator.java:133)
at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:430)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$NodeExecutor.lambda$executeRecursively$3(HierarchicalTestExecutor.java:120)
at org.junit.platform.engine.support.hierarchical.SingleTestExecutor.executeSafely(SingleTestExecutor.java:66)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$NodeExecutor.executeRecursively(HierarchicalTestExecutor.java:108)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$NodeExecutor.execute(HierarchicalTestExecutor.java:79)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$NodeExecutor.lambda$executeRecursively$2(HierarchicalTestExecutor.java:120)
at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:177)
at java.base/java.util.Iterator.forEachRemaining(Iterator.java:133)
at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:430)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$NodeExecutor.lambda$executeRecursively$3(HierarchicalTestExecutor.java:120)
at org.junit.platform.engine.support.hierarchical.SingleTestExecutor.executeSafely(SingleTestExecutor.java:66)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$NodeExecutor.executeRecursively(HierarchicalTestExecutor.java:108)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor$NodeExecutor.execute(HierarchicalTestExecutor.java:79)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:55)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:43)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:170)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:154)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:90)
at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:65)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

any idea? i think that its because some of the variable dont get initialized, but im doing adding the @Autowired on those so i dont know what it is

this is my pom file

http://maven.apache.org/xsd/maven-4.0.0.xsd"> 4.0.0

<groupId>com.praxis</groupId>
<artifactId>topics</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>

<name>topics</name>
<description>Project for Integrador 2018</description>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.10.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version>1.8</java.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-mongodb</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-rest</artifactId>
    </dependency>

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework.restdocs</groupId>
        <artifactId>spring-restdocs-mockmvc</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.datatype</groupId>
        <artifactId>jackson-datatype-jsr310</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter-api</artifactId>
        <version>RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-test</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-test</artifactId>
        <version>RELEASE</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
    </dependency>
    <dependency>
        <groupId>org.assertj</groupId>
        <artifactId>assertj-core</artifactId>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

Answer 1

For starters, if you're using JUnit Jupiter (the programming model in JUnit 5), you'll have to configure the Jupiter Test Engine in your build.

I recommend you use the official spring-boot-sample-junit-jupiter sample project as a template.

The pom.xml shows how to configure the Jupiter Test Engine with the Maven Surefire Plugin:

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <dependencies>
                <dependency>
                    <groupId>org.junit.platform</groupId>
                    <artifactId>junit-platform-surefire-provider</artifactId>
                    <version>${junit-platform.version}</version>
                </dependency>
            </dependencies>
        </plugin>
    </plugins>
</build>

Note that it also shows that you need dependency declarations for junit-jupiter-api and junit-jupiter-engine.

And SampleJunitJupiterApplicationTests shows how to configure Spring Boot's testing support with the SpringExtension for JUnit Jupiter:

@ExtendWith(SpringExtension.class)
@SpringBootTest
class TopicServiceImplTest {

  @Autowired
  TopicService service;

  // ..

}