Vintage + JUnit < 4.5 fails

[sormuras]

Overview

Vintage fails to run (here junit:junit:3.8.1 was used). A ClassNotFoundException: org.junit.runners.model.RunnerBuilder is thrown.

Aug. 24, 2018 4:04:22 VORM. org.junit.platform.launcher.core.DefaultLauncher handleThrowable
WARNING: TestEngine with ID 'junit-vintage' failed to discover tests
java.lang.NoClassDefFoundError: org/junit/runners/model/RunnerBuilder
	at org.junit.vintage.engine.discovery.VintageDiscoverer.<init>(VintageDiscoverer.java:35)
	at org.junit.vintage.engine.VintageTestEngine.discover(VintageTestEngine.java:61)
	at org.junit.platform.launcher.core.DefaultLauncher.discoverEngineRoot(DefaultLauncher.java:133)
	at org.junit.platform.launcher.core.DefaultLauncher.discoverRoot(DefaultLauncher.java:120)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:93)
	at org.junit.platform.console.tasks.ConsoleTestExecutor.executeTests(ConsoleTestExecutor.java:65)
	at org.junit.platform.console.tasks.ConsoleTestExecutor.lambda$execute$0(ConsoleTestExecutor.java:57)
	at org.junit.platform.console.tasks.CustomContextClassLoaderExecutor.invoke(CustomContextClassLoaderExecutor.java:33)
	at org.junit.platform.console.tasks.ConsoleTestExecutor.execute(ConsoleTestExecutor.java:57)
	at org.junit.platform.console.ConsoleLauncher.executeTests(ConsoleLauncher.java:97)
	at org.junit.platform.console.ConsoleLauncher.execute(ConsoleLauncher.java:87)
	at org.junit.platform.console.ConsoleLauncher.execute(ConsoleLauncher.java:49)
	at org.junit.platform.console.ConsoleLauncher.main(ConsoleLauncher.java:41)
Caused by: java.lang.ClassNotFoundException: org.junit.runners.model.RunnerBuilder
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:582)
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
	... 13 more

All JUnit versions below 4.5 should be affected: org.junit.runners.model.RunnerBuilder was introduced in 4.5

Deliverables

• Detect JUnit version < 4.12 early and throw an exception with a better error message, suggesting to update to 4.12.

[sbrannen]

We might be better off requiring JUnit >= 4.12 -- right?

[sbrannen]

... Since technically we only actively support JUnit 4.12 at the moment.

[sbrannen]

Let's keep in mind that junit-vintage-engine has a required transitive dependency on junit:junit:4.12 in its pom.xml.

Thus if a version of JUnit < 4.12 shows up on the classpath (at least in a build), that would typically be caused by some user error.

[sormuras]

Thus if a version of JUnit < 4.12 shows up on the classpath (at least in a build), that would typically be caused by some user error.

True. The exception occured when a junit:junit artifact was found on the classpath and I tried to treat that as an indicator to include and enable the JUnit Vintage engine. Will add :4.12+ to the indicator.

Providing a better error message would still be good.

[sbrannen]

Will add :4.12+ to the indicator.

Sounds good.

Providing a better error message would still be good.

Yep, I agree: better diagnostics == better software, and I added the diagnostics label to this issue accordingly. 😉