Gradle not able to run unit tests with Java 17

Question

When trying to use Java 17 with Kotlin I'm having the following issue when trying to run tests. It seems that test classes are compiled with Java 17 but Gradle is trying to run those with Java 11. The project is a simple one it is generated using start.spring.io

org.gradle.api.internal.tasks.testing.TestSuiteExecutionException: Could not execute test class 'com.test.auth.AuthApplicationTests'.
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:53)
    at [email protected]/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at [email protected]/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at [email protected]/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at [email protected]/java.lang.reflect.Method.invoke(Method.java:566)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:36)
    at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
    at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:33)
    at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)
    at com.sun.proxy.$Proxy2.processTestClass(Unknown Source)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker$2.run(TestWorker.java:176)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.executeAndMaintainThreadName(TestWorker.java:129)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:100)
    at org.gradle.api.internal.tasks.testing.worker.TestWorker.execute(TestWorker.java:60)
    at org.gradle.process.internal.worker.child.ActionExecutionWorker.execute(ActionExecutionWorker.java:56)
    at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:133)
    at org.gradle.process.internal.worker.child.SystemApplicationClassLoaderWorker.call(SystemApplicationClassLoaderWorker.java:71)
    at app//worker.org.gradle.process.internal.worker.GradleWorkerMain.run(GradleWorkerMain.java:69)
    at app//worker.org.gradle.process.internal.worker.GradleWorkerMain.main(GradleWorkerMain.java:74)
Caused by: java.lang.UnsupportedClassVersionError: com/test/auth/AuthApplicationTests has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 55.0
    at java.base/java.lang.ClassLoader.defineClass1(Native Method)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1016)
    at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:174)
    at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:802)
    at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:700)
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:623)
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:581)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
    at java.base/java.lang.Class.forName0(Native Method)
    at java.base/java.lang.Class.forName(Class.java:398)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.loadClass(JUnitPlatformTestClassProcessor.java:110)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor.access$100(JUnitPlatformTestClassProcessor.java:54)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.execute(JUnitPlatformTestClassProcessor.java:89)
    at org.gradle.api.internal.tasks.testing.junitplatform.JUnitPlatformTestClassProcessor$CollectAllTestClassesExecutor.execute(JUnitPlatformTestClassProcessor.java:79)
    at org.gradle.api.internal.tasks.testing.junit.AbstractJUnitTestClassProcessor.processTestClass(AbstractJUnitTestClassProcessor.java:62)
    at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:51)
    ... 18 more

This is how build.gradle.kts looks like:

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile

plugins {
  id("org.springframework.boot") version "2.6.2"
  id("io.spring.dependency-management") version "1.0.11.RELEASE"
  kotlin("jvm") version "1.6.10"
  kotlin("plugin.spring") version "1.6.10"
}

group = "com.test"
version = "0.0.1-SNAPSHOT"
java.sourceCompatibility = JavaVersion.VERSION_17

repositories {
  mavenCentral()
}

dependencies {
  implementation("org.springframework.boot:spring-boot-starter-actuator")
  implementation("org.springframework.boot:spring-boot-starter-security")
  implementation("org.springframework.boot:spring-boot-starter-webflux")
  implementation("com.fasterxml.jackson.module:jackson-module-kotlin")
  implementation("io.projectreactor.kotlin:reactor-kotlin-extensions")
  implementation("org.jetbrains.kotlin:kotlin-reflect")
  implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
  implementation("org.jetbrains.kotlinx:kotlinx-coroutines-reactor")
  developmentOnly("org.springframework.boot:spring-boot-devtools")
  testImplementation("org.springframework.boot:spring-boot-starter-test")
  testImplementation("io.projectreactor:reactor-test")
  testImplementation("org.springframework.security:spring-security-test")
}

tasks.withType<KotlinCompile> {
  kotlinOptions {
    freeCompilerArgs = listOf("-Xjsr305=strict")
    jvmTarget = "17"
  }
}

tasks.withType<Test> {
  useJUnitPlatform()
}

This is the test file that fails:

package com.test.auth

import org.junit.jupiter.api.Test
import org.springframework.boot.test.context.SpringBootTest

@SpringBootTest
class AuthApplicationTests {

  @Test
  fun contextLoads() {
  }

}

I kind of have all the environment variables set correctly. JAVA_HOME and JRE_HOME both are set correctly to version 17.

Answer 1

The issue was solved after adding the following config in the tests.

tasks.withType<Test> {
    useJUnitPlatform()
    val javaToolchains = project.extensions.getByType<JavaToolchainService>()
    javaLauncher.set(javaToolchains.launcherFor {
        languageVersion.set(JavaLanguageVersion.of(17))
    })
}

After going through JetBrains documentation regarding Gradle JVM toolchain support in the Kotlin plugin. Using this based on a specification, Gradle detects a locally installed JDK or JRE or downloads a requested one. Adding the following configurations solved the problem for the tests.