testNG listeners' system out/err is swallowed

does the listener work at all or its just logging not relayed?

not sure what you are asking - the listener works fine with Maven, but with Gradle it only outputs what is printed by onFinish method, completely ignoring the rest :

// ONLY this one is printed
@Override
public void onFinish(ITestContext context) { System.out.println("onFinish"); }

// the rest is ignored
@Override
public void onStart(ITestContext context) { System.out.println("onStart"); }

@Override
public void onTestStart(ITestResult result) { System.out.println("onTestStart"); }

@Override
public void onTestFailure(ITestResult result) { log(result, "failed"); }

@Override
public void onTestSkipped(ITestResult result) { log(result, "skipped"); }

@Override
public void onTestSuccess(ITestResult result) { log(result, "passed"); }

private synchronized void log(ITestResult result, String string) { System.out.println(result.getMethod() + " " + string); }

Could you please look at the github project? It demonstrates the issue.

I looked at it and it seems to me that this problem has been apparent in Gradle for some time now. E.g. even with M3 it only prints 'onFinish'. I'll update this ticket.

possibly a duplicate.