okhhtp3 mockserver java.lang.NoClassDefFoundError: okhttp3/internal/concurrent/TaskRunner$RealBackend

Question

Maven dependency

    <dependency>
        <groupId>com.squareup.okhttp3</groupId>
        <artifactId>mockwebserver</artifactId>
        <version>4.9.0</version>
        <scope>test</scope>
    </dependency>

The test I've written

@SpringJUnitConfig(classes = {GithubApiService.class, WebClientConfiguration.class})
@EnableAutoConfiguration
public class GithubApiServiceTest {

    @Test
    public void testGithubResponseJsonToMapConversion(
            @Autowired GithubApiService service,
            @Value("classpath:github/commit-payload.json") Resource commitPayloadFile) throws IOException {

        final String COMMITS_URL = "/repos/Codertocat/Hello-World/commits/sha";

        //Stub response from Github Server
        String responseJson = new ObjectMapper().writeValueAsString(
                new String(Files.readAllBytes(Paths.get(commitPayloadFile.getFile().getAbsolutePath()))));
        MockWebServer server = new MockWebServer();
        server.enqueue(new MockResponse()
                               .addHeader("Content-Type", "application/json; charset=utf-8")
                               .setBody(responseJson)
                               .setResponseCode(OK.value()));
        server.start();
        // Get mock server's URL
        HttpUrl mockGithubUrl = server.url(COMMITS_URL);

        //Call API Service
        Map<String, Object> result = service.getCommitDetails(mockGithubUrl.toString()).block();

        //Expect return type is hashmap
        assertThat(result.get("sha")).isEqualTo("6dcb09b5b57875f334f61aebed695e2e4193db5e");

        server.shutdown();
    }
}

The class under test

@Service
@AllArgsConstructor(onConstructor = @__(@Autowired))
public class GithubApiService {

    @Autowired
    private final WebClient webClient;

    public Mono<Map<String, Object>> getCommitDetails(String commitsUrl) {
        return webClient.get()
                .uri(commitsUrl)
                .httpRequest(httpRequest -> {
                    HttpClientRequest reactorRequest = httpRequest.getNativeRequest();
                    reactorRequest.responseTimeout(Duration.ofSeconds(2));
                })
                .accept(APPLICATION_JSON)
                .retrieve()
                .bodyToMono(new ParameterizedTypeReference<Map<String, Object>>() {
                });
    }
}

I get this error when I run the test

java.lang.NoClassDefFoundError: okhttp3/internal/concurrent/TaskRunner$RealBackend

    at okhttp3.mockwebserver.MockWebServer.<init>(MockWebServer.kt:101)
    at com.digite.vcs.git.analytics.github.webhook.GithubApiServiceTest.testGithubResponseJsonToMapConversion(GithubApiServiceTest.java:37)
    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.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:688)
    at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
    at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
    at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
    at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
    at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
    at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:210)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:206)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:131)
    at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:65)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:143)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:129)
    at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:127)
    at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:126)
    at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:84)
    at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
    at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:108)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
    at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:96)
    at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:75)
    at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)
Caused by: java.lang.ClassNotFoundException: okhttp3.internal.concurrent.TaskRunner$RealBackend
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
    ... 67 more

When I browse on source TaskRunner on github I do see the TaskRunner class but not when I search for it from within my IDE. Am I missing something in the dependency declaration?

[INFO] --- maven-dependency-plugin:3.1.2:tree (default-cli) @ git-analytics ---
[INFO] com.digite.vcs:git-analytics:jar:0.0.1-SNAPSHOT
[INFO] +- org.springframework.boot:spring-boot-starter-web:jar:2.4.1:compile
[INFO] |  +- org.springframework.boot:spring-boot-starter:jar:2.4.1:compile
[INFO] |  |  +- org.springframework.boot:spring-boot:jar:2.4.1:compile
[INFO] |  |  +- org.springframework.boot:spring-boot-autoconfigure:jar:2.4.1:compile
[INFO] |  |  +- org.springframework.boot:spring-boot-starter-logging:jar:2.4.1:compile
[INFO] |  |  |  +- ch.qos.logback:logback-classic:jar:1.2.3:compile
[INFO] |  |  |  |  \- ch.qos.logback:logback-core:jar:1.2.3:compile
[INFO] |  |  |  +- org.apache.logging.log4j:log4j-to-slf4j:jar:2.13.3:compile
[INFO] |  |  |  |  \- org.apache.logging.log4j:log4j-api:jar:2.13.3:compile
[INFO] |  |  |  \- org.slf4j:jul-to-slf4j:jar:1.7.30:compile
[INFO] |  |  +- jakarta.annotation:jakarta.annotation-api:jar:1.3.5:compile
[INFO] |  |  \- org.yaml:snakeyaml:jar:1.27:compile
[INFO] |  +- org.springframework.boot:spring-boot-starter-json:jar:2.4.1:compile
[INFO] |  |  +- com.fasterxml.jackson.datatype:jackson-datatype-jdk8:jar:2.11.3:compile
[INFO] |  |  +- com.fasterxml.jackson.datatype:jackson-datatype-jsr310:jar:2.11.3:compile
[INFO] |  |  \- com.fasterxml.jackson.module:jackson-module-parameter-names:jar:2.11.3:compile
[INFO] |  +- org.springframework.boot:spring-boot-starter-tomcat:jar:2.4.1:compile
[INFO] |  |  +- org.apache.tomcat.embed:tomcat-embed-core:jar:9.0.41:compile
[INFO] |  |  +- org.glassfish:jakarta.el:jar:3.0.3:compile
[INFO] |  |  \- org.apache.tomcat.embed:tomcat-embed-websocket:jar:9.0.41:compile
[INFO] |  +- org.springframework:spring-web:jar:5.3.2:compile
[INFO] |  |  \- org.springframework:spring-beans:jar:5.3.2:compile
[INFO] |  \- org.springframework:spring-webmvc:jar:5.3.2:compile
[INFO] |     +- org.springframework:spring-aop:jar:5.3.2:compile
[INFO] |     +- org.springframework:spring-context:jar:5.3.2:compile
[INFO] |     \- org.springframework:spring-expression:jar:5.3.2:compile
[INFO] +- org.springframework.boot:spring-boot-starter-webflux:jar:2.4.1:compile
[INFO] |  +- org.springframework.boot:spring-boot-starter-reactor-netty:jar:2.4.1:compile
[INFO] |  |  \- io.projectreactor.netty:reactor-netty-http:jar:1.0.2:compile
[INFO] |  |     +- io.netty:netty-codec-http:jar:4.1.55.Final:compile
[INFO] |  |     |  +- io.netty:netty-common:jar:4.1.55.Final:compile
[INFO] |  |     |  +- io.netty:netty-buffer:jar:4.1.55.Final:compile
[INFO] |  |     |  +- io.netty:netty-transport:jar:4.1.55.Final:compile
[INFO] |  |     |  +- io.netty:netty-codec:jar:4.1.55.Final:compile
[INFO] |  |     |  \- io.netty:netty-handler:jar:4.1.55.Final:compile
[INFO] |  |     +- io.netty:netty-codec-http2:jar:4.1.55.Final:compile
[INFO] |  |     +- io.netty:netty-resolver-dns:jar:4.1.55.Final:compile
[INFO] |  |     |  +- io.netty:netty-resolver:jar:4.1.55.Final:compile
[INFO] |  |     |  \- io.netty:netty-codec-dns:jar:4.1.55.Final:compile
[INFO] |  |     +- io.netty:netty-transport-native-epoll:jar:linux-x86_64:4.1.55.Final:compile
[INFO] |  |     |  \- io.netty:netty-transport-native-unix-common:jar:4.1.55.Final:compile
[INFO] |  |     \- io.projectreactor.netty:reactor-netty-core:jar:1.0.2:compile
[INFO] |  |        \- io.netty:netty-handler-proxy:jar:4.1.55.Final:compile
[INFO] |  |           \- io.netty:netty-codec-socks:jar:4.1.55.Final:compile
[INFO] |  \- org.springframework:spring-webflux:jar:5.3.2:compile
[INFO] |     \- io.projectreactor:reactor-core:jar:3.4.1:compile
[INFO] |        \- org.reactivestreams:reactive-streams:jar:1.0.3:compile
[INFO] +- org.springframework.boot:spring-boot-starter-data-mongodb:jar:2.4.1:compile
[INFO] |  +- org.mongodb:mongodb-driver-sync:jar:4.1.1:compile
[INFO] |  |  +- org.mongodb:bson:jar:4.1.1:compile
[INFO] |  |  \- org.mongodb:mongodb-driver-core:jar:4.1.1:compile
[INFO] |  \- org.springframework.data:spring-data-mongodb:jar:3.1.2:compile
[INFO] |     +- org.springframework:spring-tx:jar:5.3.2:compile
[INFO] |     \- org.springframework.data:spring-data-commons:jar:2.4.2:compile
[INFO] +- com.fasterxml.jackson.core:jackson-databind:jar:2.11.3:compile
[INFO] |  +- com.fasterxml.jackson.core:jackson-annotations:jar:2.11.3:compile
[INFO] |  \- com.fasterxml.jackson.core:jackson-core:jar:2.11.3:compile
[INFO] +- org.projectlombok:lombok:jar:1.18.16:compile (optional) 
[INFO] +- org.springframework.boot:spring-boot-starter-test:jar:2.4.1:test
[INFO] |  +- org.springframework.boot:spring-boot-test:jar:2.4.1:test
[INFO] |  +- org.springframework.boot:spring-boot-test-autoconfigure:jar:2.4.1: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:3.18.1:test
[INFO] |  +- org.hamcrest:hamcrest:jar:2.2:test
[INFO] |  +- org.junit.jupiter:junit-jupiter:jar:5.7.0:test
[INFO] |  |  +- org.junit.jupiter:junit-jupiter-api:jar:5.7.0:test
[INFO] |  |  |  +- org.apiguardian:apiguardian-api:jar:1.1.0:test
[INFO] |  |  |  +- org.opentest4j:opentest4j:jar:1.2.0:test
[INFO] |  |  |  \- org.junit.platform:junit-platform-commons:jar:1.7.0:test
[INFO] |  |  +- org.junit.jupiter:junit-jupiter-params:jar:5.7.0:test
[INFO] |  |  \- org.junit.jupiter:junit-jupiter-engine:jar:5.7.0:test
[INFO] |  |     \- org.junit.platform:junit-platform-engine:jar:1.7.0:test
[INFO] |  +- org.mockito:mockito-core:jar:3.6.28:test
[INFO] |  |  +- net.bytebuddy:byte-buddy:jar:1.10.18:test
[INFO] |  |  +- net.bytebuddy:byte-buddy-agent:jar:1.10.18:test
[INFO] |  |  \- org.objenesis:objenesis:jar:3.1:test
[INFO] |  +- org.mockito:mockito-junit-jupiter:jar:3.6.28:test
[INFO] |  +- org.skyscreamer:jsonassert:jar:1.5.0:test
[INFO] |  |  \- com.vaadin.external.google:android-json:jar:0.0.20131108.vaadin1:test
[INFO] |  +- org.springframework:spring-core:jar:5.3.2:compile
[INFO] |  |  \- org.springframework:spring-jcl:jar:5.3.2:compile
[INFO] |  +- org.springframework:spring-test:jar:5.3.2:test
[INFO] |  \- org.xmlunit:xmlunit-core:jar:2.7.0:test
[INFO] +- de.flapdoodle.embed:de.flapdoodle.embed.mongo:jar:2.2.0:test
[INFO] |  \- de.flapdoodle.embed:de.flapdoodle.embed.process:jar:2.1.2:test
[INFO] |     +- org.apache.commons:commons-lang3:jar:3.11:test
[INFO] |     +- net.java.dev.jna:jna:jar:4.0.0:test
[INFO] |     +- net.java.dev.jna:jna-platform:jar:4.0.0:test
[INFO] |     \- org.apache.commons:commons-compress:jar:1.18:test
[INFO] +- com.jayway.jsonpath:json-path:jar:2.4.0:test
[INFO] |  +- net.minidev:json-smart:jar:2.3:test
[INFO] |  |  \- net.minidev:accessors-smart:jar:1.2:test
[INFO] |  |     \- org.ow2.asm:asm:jar:5.0.4:test
[INFO] |  \- org.slf4j:slf4j-api:jar:1.7.30:compile
[INFO] \- com.squareup.okhttp3:mockwebserver:jar:4.9.0:test
[INFO]    +- com.squareup.okhttp3:okhttp:jar:3.14.9:test
[INFO]    |  \- com.squareup.okio:okio:jar:1.17.2:test
[INFO]    +- junit:junit:jar:4.13.1:test
[INFO]    |  \- org.hamcrest:hamcrest-core:jar:2.2:test
[INFO]    \- org.jetbrains.kotlin:kotlin-stdlib-jdk8:jar:1.4.21:test
[INFO]       +- org.jetbrains.kotlin:kotlin-stdlib:jar:1.4.21:test
[INFO]       |  +- org.jetbrains.kotlin:kotlin-stdlib-common:jar:1.4.21:test
[INFO]       |  \- org.jetbrains:annotations:jar:13.0:test
[INFO]       \- org.jetbrains.kotlin:kotlin-stdlib-jdk7:jar:1.4.21:test

Answer 1

You're using OkHttp 3.14.9 with MockWebServer 4.9.0. These versions gotta match.

Answer 2

I solved the issue by excluding embedded default okhttp v3.14.9

testImplementation("com.squareup.okhttp3:mockwebserver:4.9.0") {
    exclude("com.squareup.okhttp3", "okhttp")
}
testImplementation("com.squareup.okhttp3:okhttp:4.9.0")

Answer 3

If you don't have a specific reason for a specific version, don't specify it in the POM file and leave it for Maven to decide.

The version is set in the <dependencyManagement> of the org.springframework.boot/spring-boot-dependencies. It is set consistently with other related dependencies and there rarely is a legitimate reason to change it.

Then the versions of the transitive dependencies will not collide.

In your POM this should be enough:

<dependency>
    <groupId>com.squareup.okhttp3</groupId>
    <artifactId>mockwebserver</artifactId>
    <scope>test</scope>
</dependency>