Improve debug mode detection in JUnit Jupiter

[cj81499]

Overview

I'm handling an upgrade from JUnit 4 to JUnit 5 and noticed that disabling our timeouts with -Djunit.jupiter.execution.timeout.mode=disabled_on_debug is not working as expected.

We use VSCode as our editor/IDE. When using the Debugger for Java extension to debug tests.

When ran in my project, the following "test" prints [-ea, -Djunit.jupiter.execution.timeout.mode=disabled_on_debug, -XX:+ShowCodeDetailsInExceptionMessages, -Dfile.encoding=UTF-8]

When ran with the debugger in my project, the following "test" prints [-Xdebug, -Xnoagent, -Djava.compiler=NONE, -Xrunjdwp:transport=dt_socket,address=localhost:34399,server=n,suspend=y, -ea, -Djunit.jupiter.execution.timeout.mode=disabled_on_debug, -XX:+ShowCodeDetailsInExceptionMessages, -Dfile.encoding=UTF-8]

@Test
void test() {
  System.out.println(ManagementFactory.getRuntimeMXBean().getInputArguments());
}

Notably, the first 4 argument of the output from the run using the debugger are not present from the run without the debugger.

JUnit 4 detected -Xdebug as a sign of debugging, but (prior to this change) JUnit 5 does not, leading to the unexpected timeouts while debugging (and regression, compared to JUnit 4). Since JUnit 4 used it, I figured -Xdebug was the best thing to detect.

I'm not really sure how to test this kind of thing, but I'm open to suggestions.

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Definition of Done

• There are no TODOs left in the code
• Method preconditions are checked and documented in the method's Javadoc
• Coding conventions (e.g. for logging) have been followed
• Change is covered by automated tests including corner cases, errors, and exception handling
• Public API has Javadoc and @API annotations
• Change is documented in the User Guide and Release Notes
• All continuous integration builds pass

[sbrannen]

Since JUnit 4 used it, I figured -Xdebug was the best thing to detect.

I don't recall the details, but I believe that was not picked for a reason.

It might be better to just check if one of the arguments contains jdwp (see Java Debug Wire Protocol.

That would then work for -Xrunjdwp as well as -agentlib:jdwp.

[sbrannen]

related discussion in #2026 (comment)

[cj81499]

Thanks for the feedback. I expect I'll have time to fix this up on Monday.

Any input on writing tests? Or are you comfortable without?

[sbrannen]

Any input on writing tests? Or are you comfortable without?

It appears we don't have any tests for that (at least not with the initial commit ddb8c61), so I guess it will be OK without additional tests for this particular feature.

[marcphilipp]

@cj81499 Thanks for your contribution! 👍

[cj81499]

@marcphilipp thanks for your help getting it merged!
Selfishly, I'm happy to have it fixed :)