Spring Boot RestController Testclass doesn't instantiate Mocked Variables - spring-boot

Question

I'm trying to create a Unit Test for a RestController in Spring Boot.
The Controller looks something like this:
#RestController()
#RequestMapping("/endpoint")
public class MyRestController {
#Autowired
private MyService service;
#GetMapping(value = "/{id}", produces = "application/json")
public ResponseEntity<String> findSomethingById(#PathVariable("id") String id, #RequestParam("param1")String param1) throws MyServiceException {
return ResponseEntity.ok(service.findSomethingById(id,param1));
}
And the Unit Test Class looks as follows:
import org.junit.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
import org.springframework.boot.test.mock.mockito.MockBean;
import org.springframework.http.MediaType;
import org.springframework.test.context.junit.jupiter.SpringExtension;
import org.springframework.test.web.servlet.MockMvc;
import static org.hamcrest.Matchers.hasSize;
import static org.hamcrest.Matchers.isA;
import static org.mockito.Mockito.when;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
#ExtendWith(SpringExtension.class)
#WebMvcTest(MyRestController.class)
public class MyRestControllerUnitTest {
#Autowired
private MockMvc mockMvc;
#MockBean
private MyService service;
#Test
public void testGetSomethingId() throws Exception {
when(service.findSomethingById("1", "something")).thenReturn("found");
mockMvc.perform(get("/endpoint/1").param("param1","something"))
.andDo(print())
.andExpect(status().isOk());
// some more Expects
}
}
The issue is that both the service and the mockMvc Variables are null during the execution of the Test, but shouldn't be as they should get intantiated by Spring according to their Annotations according to my Understanding.
Looking for similair issues I found mostly issues where Junit4 and Junit5 got mixed togehter, which seems not to be my problem.
Sample question I found NullPointerException on controller when testing in SpringBoot API - Mocking
I'm using Spring Boot 2.7.4 as well as Java 11 and I added the spring-boot-starter-test dependency to my pom.xml for the Test dependencies
Below is the StackTrace I get when executing the Test with my IDEA:
java.lang.NullPointerException
at MyRestControllerUnitTest.findSomethingById(Line of when() as service is null and so is mockMvc)
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:566)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
at org.junit.vintage.engine.execution.RunnerExecutor.execute(RunnerExecutor.java:42)
at org.junit.vintage.engine.VintageTestEngine.executeAllChildren(VintageTestEngine.java:80)
at org.junit.vintage.engine.VintageTestEngine.execute(VintageTestEngine.java:72)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53)
at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Process finished with exit code -1
MainClass:
#SpringBootApplication
public class MyApplication {
public static void main(String[] args) {
SpringApplication.run(MyApplication.class, args);
}
}
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.7.4</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>org.myGroup</groupId>
<artifactId>myArtifact</artifactId>
<version>1.0.0-SNAPSHOT</version>
<name>MyApplication</name>
<properties>
<java.version>11</java.version>
<spring-cloud.version>2020.0.3</spring-cloud.version>
<start-class>org.main.MyApplication</start-class>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-core</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-tomcat</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
</dependency>
<dependency>
<groupId>org.springdoc</groupId>
<artifactId>springdoc-openapi-ui</artifactId>
<version>1.6.12</version>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<exclusions>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-configuration-processor</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-webflux</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>
<dependency>
<groupId>javax.validation</groupId>
<artifactId>validation-api</artifactId>
</dependency>
<dependency>
<groupId>org.hibernate.validator</groupId>
<artifactId>hibernate-validator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<executions>
<execution>
<goals>
<goal>repackage</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-source-plugin</artifactId>
<configuration>
<archive>
<manifest>
<mainClass>org.main.MyApplication</mainClass>
</manifest>
</archive>
</configuration>
<executions>
<execution>
<id>attach-sources</id>
<goals>
<goal>jar</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>

Answer 1

The issue is coming because of the #Test annotation. You are using this annotation from the org.junit.Test package that is part of Junit4. Other annotations used in the test case are part of Junit5. So this is conflicting. Please use #Test annotation from the org.junit.jupiter.api.Test package and try again.
Also, remove this dependency from the pom.xml
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>

Answer 2

Adding to the answer by Rohit Agarwal, if you run
./mvw dependency:tree
You shall see transitive dependencies added by the spring-boot-test
\- org.springframework.boot:spring-boot-starter-test:jar:2.7.5:test
[INFO] +- org.springframework.boot:spring-boot-test:jar:2.7.5:test
[INFO] +- org.springframework.boot:spring-boot-test autoconfigure:jar:2.7.5:test
[INFO] +- com.jayway.jsonpath:json-path:jar:2.7.0:test
[INFO] | \- net.minidev:json-smart:jar:2.4.8:test
[INFO] | \- net.minidev:accessors-smart:jar:2.4.8:test
[INFO] | \- org.ow2.asm:asm:jar:9.1:test
[INFO] +- jakarta.xml.bind:jakarta.xml.bind-api:jar:2.3.3:test
[INFO] | \- jakarta.activation:jakarta.activation-api:jar:1.2.2:test
[INFO] +- org.assertj:assertj-core:jar:3.22.0:test
[INFO] +- org.hamcrest:hamcrest:jar:2.2:test
[INFO] +- org.junit.jupiter:junit-jupiter:jar:5.8.2:test <------------- Note this
[INFO] | +- org.junit.jupiter:junit-jupiter-api:jar:5.8.2:test
JUnit 5 added by spring-boot-test as a transitive dependency as shown above.
Since Springboot 2.4 Junit4 Vintage engine is removed.
Hence you should use the Junit5 Test annotation org.junit.jupiter.api.Test