That was one ugly bug... luckily I had experienced something like this using PHPUnit some years ago:
Quoting from my patch:
// As PHPUnit runs all tests in one run, there might be some loggers left over
// from previous runs. ResetConfiguration() only clears the appenders, it does
// not remove the categories!
That explains why a simple "phpunit configurators/LoggerConfiguratorBasicTest" always succeeded but a "mvn test" at least for me never.
Using print_r I could see two loggers named "test" and "mylogger", strings that are used as logger names in completely different test files.