[SOLVED] org.junit.platform.commons.JUnitException: TestEngine with ID 'junit-jupiter' failed to discover tests

I wan to implement a Junit 5 test into Gradle project. I tried this:

Gradle configuration:

plugins {
    id 'org.springframework.boot' version '2.5.5'
    id 'io.spring.dependency-management' version '1.0.11.RELEASE'
    id 'java'
}

group = 'test'
version = '0.0.1'
sourceCompatibility = '17'

repositories {
    mavenCentral()
}

ext {
    set('springCloudVersion', "2020.0.4")
}

dependencies {
    ...............
    testImplementation 'org.springframework.boot:spring-boot-starter-test'
    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.8.2'
    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.8.2'
}

dependencyManagement {
    imports {
        mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}"
    }
}

test {
    useJUnitPlatform()
}

Junit test:

import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.Timeout;

import java.util.concurrent.TimeUnit;

public class GeneratePdf {

    @DisplayName("Test MessageService.get()")
    @Test
    @Timeout(value = 60, unit = TimeUnit.SECONDS)
    public void generatePdfFileTes() throws InterruptedException
    {
        System.out.println("test!");
    }

}

When I run the code I get error:

Internal Error occurred.
org.junit.platform.commons.JUnitException: TestEngine with ID 'junit-jupiter' failed to discover tests
    at org.junit.platform.launcher.core.EngineDiscoveryOrchestrator.discoverEngineRoot(EngineDiscoveryOrchestrator.java:160)
    at org.junit.platform.launcher.core.EngineDiscoveryOrchestrator.discoverSafely(EngineDiscoveryOrchestrator.java:134)
    at org.junit.platform.launcher.core.EngineDiscoveryOrchestrator.discover(EngineDiscoveryOrchestrator.java:108)
    at org.junit.platform.launcher.core.EngineDiscoveryOrchestrator.discover(EngineDiscoveryOrchestrator.java:80)
    at org.junit.platform.launcher.core.DefaultLauncher.discover(DefaultLauncher.java:110)
    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)
Caused by: org.junit.platform.commons.JUnitException: MethodSelector [className = 'org.merchant.poc.GeneratePdf', methodName = 'generatePdfFileTes', methodParameterTypes = ''] resolution failed
    at org.junit.platform.launcher.listeners.discovery.AbortOnFailureLauncherDiscoveryListener.selectorProcessed(AbortOnFailureLauncherDiscoveryListener.java:39)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution.resolveCompletely(EngineDiscoveryRequestResolution.java:102)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution.run(EngineDiscoveryRequestResolution.java:82)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolver.resolve(EngineDiscoveryRequestResolver.java:113)
    at org.junit.jupiter.engine.discovery.DiscoverySelectorResolver.resolveSelectors(DiscoverySelectorResolver.java:46)
    at org.junit.jupiter.engine.JupiterTestEngine.discover(JupiterTestEngine.java:69)
    at org.junit.platform.launcher.core.EngineDiscoveryOrchestrator.discoverEngineRoot(EngineDiscoveryOrchestrator.java:152)
    ... 13 more
Caused by: org.junit.platform.commons.PreconditionViolationException: Could not load class with name: org.merchant.poc.GeneratePdf
    at org.junit.platform.engine.discovery.MethodSelector.lambda$lazyLoadJavaClass$0(MethodSelector.java:157)
    at org.junit.platform.commons.function.Try$Failure.getOrThrow(Try.java:335)
    at org.junit.platform.engine.discovery.MethodSelector.lazyLoadJavaClass(MethodSelector.java:156)
    at org.junit.platform.engine.discovery.MethodSelector.getJavaClass(MethodSelector.java:135)
    at org.junit.jupiter.engine.discovery.MethodSelectorResolver.resolve(MethodSelectorResolver.java:73)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution.lambda$resolve$2(EngineDiscoveryRequestResolution.java:146)
    at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
    at java.base/java.util.ArrayList$ArrayListSpliterator.tryAdvance(ArrayList.java:1602)
    at java.base/java.util.stream.ReferencePipeline.forEachWithCancel(ReferencePipeline.java:129)
    at java.base/java.util.stream.AbstractPipeline.copyIntoWithCancel(AbstractPipeline.java:527)
    at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:513)
    at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
    at java.base/java.util.stream.FindOps$FindOp.evaluateSequential(FindOps.java:150)
    at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.base/java.util.stream.ReferencePipeline.findFirst(ReferencePipeline.java:647)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution.resolve(EngineDiscoveryRequestResolution.java:185)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution.resolve(EngineDiscoveryRequestResolution.java:125)
    at org.junit.platform.engine.support.discovery.EngineDiscoveryRequestResolution.resolveCompletely(EngineDiscoveryRequestResolution.java:91)
    ... 18 more
Caused by: java.lang.ClassNotFoundException: org.merchant.poc.GeneratePdf
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:520)
    at org.junit.platform.commons.util.ReflectionUtils.lambda$tryToLoadClass$9(ReflectionUtils.java:829)
    at org.junit.platform.commons.function.Try.lambda$call$0(Try.java:57)
    at org.junit.platform.commons.function.Try.of(Try.java:93)
    at org.junit.platform.commons.function.Try.call(Try.java:57)
    at org.junit.platform.commons.util.ReflectionUtils.tryToLoadClass(ReflectionUtils.java:792)
    at org.junit.platform.commons.util.ReflectionUtils.tryToLoadClass(ReflectionUtils.java:748)
    ... 34 more

Do you know how this issue can be fixed?

EDIT:

import org.junit.jupiter.api.Test;

public class InvoiceTests {

    @Test
    public void generateTest()
    {
        System.out.println("test!");
    }

}

I tried this but again it's not working.