NoClassDefFoundError for PreconditionViolationException when running JUnit5 tests

[michalhosala]

I can no longer run unit tests for my spring app within VSCode IDE, am only getting the following error when trying to do so:

java.lang.NoClassDefFoundError: org/junit/platform/commons/PreconditionViolationException
	at org.eclipse.jdt.internal.junit5.runner.JUnit5TestLoader.createTest(JUnit5TestLoader.java:90)
	at org.eclipse.jdt.internal.junit5.runner.JUnit5TestLoader.loadTests(JUnit5TestLoader.java:48)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:526)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:770)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:464)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:210)
Caused by: java.lang.ClassNotFoundException: org.junit.platform.commons.PreconditionViolationException
	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)

PreconditionViolationException is now deprecated, see here, so it would seem Java Test Runner is not aware of it or what. Currently my build.gradle has junit dependencies like this:

        testImplementation "org.junit.jupiter:junit-jupiter-api:5.6.0"
        testImplementation "org.junit.jupiter:junit-jupiter-params:5.6.0"
        testImplementation "org.springframework.boot:spring-boot-starter-test:2.2.8.RELEASE"
        testRuntime "org.junit.jupiter:junit-jupiter-engine:5.6.0"

I had a look at what seemed like a related issue but none of the workarounds from there worked for me.

[jdneo]

Would you mind to share a sample project to us?

Test Runner is not responsible to resolve the classpath so I guess there's something wrong with the upstream side. (Maybe buildship) I need a sample project to repro the issue and then take a look where is the gap

[michalhosala]

Hi @jdneo , I can't share my exact project, but I made a stripped down version to reproduce the issue. See here:
https://drive.google.com/file/d/1ou7yTyjmeFqmXrkhid0k7DqGP3tJ06-J/view?usp=sharing

Seems like when I remove the following from build.gradle, things start to work, but I have to be on jdk 11:

ext {
    jdkVersion = "11"
}

Thanks for having a look!

[jdneo]

Please try the following configurations:

dependencies {
    implementation "org.springframework.boot:spring-boot-starter-jetty:2.1.5.RELEASE"
    implementation "org.springframework.boot:spring-boot-starter-thymeleaf:2.1.5.RELEASE"
    implementation ("org.springframework.boot:spring-boot-starter-web:2.1.5.RELEASE") {
        exclude group: "org.springframework.boot", module: "spring-boot-starter-tomcat"
    }
    runtimeOnly "org.springframework.boot:spring-boot-devtools:2.1.5.RELEASE"
    testImplementation "org.hamcrest:hamcrest-library:2.1"
    testImplementation "org.junit.jupiter:junit-jupiter:5.6.0"
    testImplementation "org.springframework.boot:spring-boot-starter-test:2.1.5.RELEASE"
    compile "org.junit.platform:junit-platform-commons:1.6.0"
    testCompile "org.junit.platform:junit-platform-engine:1.6.0"
}

[michalhosala]

@jdneo your workaround enabled me to run the tests in VS code. Any idea where is the actual problem and how to address it?

[michalhosala]

Hmm, I guess too soon. When I applied this remedy to my original project, not just a demo, it started throwing another error, again related to preconditions:

java.lang.IllegalArgumentException: Error: test loader org.eclipse.jdt.internal.junit5.runner.JUnit5TestLoader not found:
org.junit.platform.commons.PreconditionViolationException: Cannot create Launcher without at least one TestEngine; consider adding an engine implementation JAR to the classpath
	at org.junit.platform.commons.util.Preconditions.condition(Preconditions.java:296)
	at org.junit.platform.launcher.core.DefaultLauncher.<init>(DefaultLauncher.java:62)
	at org.junit.platform.launcher.core.LauncherFactory.create(LauncherFactory.java:91)
	at org.junit.platform.launcher.core.LauncherFactory.create(LauncherFactory.java:67)
	at org.eclipse.jdt.internal.junit5.runner.JUnit5TestLoader.<init>(JUnit5TestLoader.java:34)
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490)
	at java.base/java.lang.Class.newInstance(Class.java:584)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.createRawTestLoader(RemoteTestRunner.java:371)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.createLoader(RemoteTestRunner.java:366)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.defaultInit(RemoteTestRunner.java:310)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.init(RemoteTestRunner.java:225)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)

	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.createRawTestLoader(RemoteTestRunner.java:376)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.createLoader(RemoteTestRunner.java:366)
java.lang.IllegalArgumentException: Error: test loader org.eclipse.jdt.internal.junit5.runner.JUnit5TestLoader not found:
org.junit.platform.commons.PreconditionViolationException: Cannot create Launcher without at least one TestEngine; consider adding an engine implementation JAR to the classpath
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.defaultInit(RemoteTestRunner.java:310)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.init(RemoteTestRunner.java:225)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)

It went away after I put the following dependency back as well:

testRuntime "org.junit.jupiter:junit-jupiter-engine:5.3.2"

[jdneo]

I guess all of the problem is about the classpath. What I did is find where the missing class comes from and add them into the dependecies.

Could I understand the problem has been solved now?

[michalhosala]

@jdneo but the problem was not present before vs code update / extension update,on top of that the code is working fine outside of the VS code, in intelliJ, from command line etc. So the problem is not "solved" for VS code, just "worked around". As I already wrote in my first comment, "PreconditionViolationException is now deprecated" so I don't think correct solution is to try and patch the missing classes but rather accommodate for the class being deprecated.

[pumano]

@michalhosala I got this too but problem is in junit jupiter, some libs absent and testImplementation "org.junit.jupiter:junit-jupiter:5.6.0" fix it. Because it contains all libs. But second error is about testImplementation "org.junit.jupiter:junit-jupiter-engine:5.6.0" which is not exist too. Just add it.

[sagar-bhatt-tide]

I am getting this error after every fix mentioned above

org.eclipse.jdt.internal.junit5.runner.JUnit5TestLoader not found

[github-actions]

Hi @michalhosala, I'm an AI Support assistant here to help with your issue. While the team reviews your request, I wanted to provide some possible tips and documentation that might help you in the meantime.

Suggestions to resolve NoClassDefFoundError for PreconditionViolationException

• Upgrade JUnit to match the Test Runner
  The VS Code Java Test Runner’s Eclipse JUnit5 loader may expect a newer junit-platform-commons version. In your Gradle build, replace the separate modules with the bundled artifact and align versions, e.g.:

  testImplementation 'org.junit.jupiter:junit-jupiter:5.7.2'
  testRuntimeOnly   'org.junit.jupiter:junit-jupiter-engine:5.7.2'

  (this transitively brings in junit-platform-commons:1.7.2 which contains PreconditionViolationException).

• Or explicitly add junit-platform-commons
  If you must stay on JUnit 5.6.x, add:

  testRuntimeOnly 'org.junit.platform:junit-platform-commons:1.7.2'

  so the missing class is on the test runtime classpath.

• Sync VS Code’s Java classpath
  After editing build.gradle, click Now or Always on the “A build file was modified…” prompt, or run Java: Clean Java Language Server Workspace and reload the window.

• Update Java Test Runner extension
  Ensure you’re on the latest vscode-java-test to get the most recent JUnit5 support.

Other references with low confidence

vscode-java-test#971

• Title: JUnit Platform missing from classpath in VS Code Test Runner
• Description: Similar missing-class errors when the console runner jars aren’t on the classpath.
• URL: NoClassDefFoundError when running JUnit5 tests #971

The team will respond to your issue shortly. I hope these suggestions are helpful in the meantime. If this comment helped you, please give it a 👍. If the suggestion was not helpful or incorrect, please give it a 👎. Your feedback helps us improve!