Weird JUnit logging behavior

Question

I'm noticing some weird behavior using standard logging during JUnit tests. Does JUnit redirect standard output to a different stream? How can I get access to that?

Here's a simple JUnit test that demonstrates the behavior I'm describing.

@Test
public void logMessage() {
    // set up new logger with output directed to standard out
    Logger logger = Logger.getLogger("my.test.logger");
    logger.addHandler(new StreamHandler(System.out, new SimpleFormatter()));

    // log a warning message
    logger.warning("logger message"); // message 1

    // turn off parent handlers
    logger.setUseParentHandlers(false);

    // log a second warning message
    logger.warning("second logger message"); // message 2

    // print somehting to standard output
    System.out.println("standard output message");  //message 3
}

Notice that I've created a new logger that simply sends its log messages to standard output (System.out).

Here's the Junit output

Testsuite: com.my.FormatterTest
Feb 19, 2009 12:02:33 PM com.my.FormatterTest logMessage
WARNING: logger message
standard output message
Tests run: 1, Failures: 0, Errors: 0, Time elapsed: 0.079 sec

------------- Standard Output ---------------
standard output message
------------- ---------------- ---------------
------------- Standard Error -----------------
Feb 19, 2009 12:02:33 PM com.my.FormatterTest logMessage
WARNING: logger message
------------- ---------------- ---------------
Feb 19, 2009 12:02:33 PM com.my.FormatterTest logMessage
WARNING: logger message
Feb 19, 2009 12:02:33 PM com.my.FormatterTest logMessage
WARNING: second logger message
test:
BUILD SUCCESSFUL (total time: 2 seconds)

Why don't message 1 or message 2 show up in the Standard Output portion of the JUnit output?

Thanks!

Answer 1

As you indirectly suggest, the junit testrunners redirect stdout and stderr to a separate stream while the test is running. Your logger is normally initialized before this redirection occurs, which means it uses the regular System.out/System.err for logging to console.

This can be fairly easily seen by looking at the source for the JunitTestRunner class.

Edit: I have looked at some of the source code because your question made me curious. I do not know which TestRunner you are using, and the answer may lay there; the stream redirections etc are not a part of the junit framework but are implemented by ant/eclipse/maven/idea. It looks like you addHandler has no effect whatsovever , so I suspect something is intercepting it (your output would be logical if all the logging was done by a parent logger).