@BeforeClass
  public static void setUpLogConfigFile() throws Exception {
    configFile = new File(temporaryFolder.getRoot(), CONFIG_FILE_NAME);
    configFilePath = configFile.getAbsolutePath();
    writeSimpleConfigFile(configFile, Level.WARN);
  }
This config file is generated dynamically by the test class.
geode-log4j/src/integrationTest/java/org/apache/geode/logging/log4j/internal/impl/FastLoggerIntegrationTest.java