public static long getSessionAgeSum() {
		if (!instanceCreated) {
			return -1;
		}
		final long now = System.currentTimeMillis();
		long result = 0;
		for (final HttpSession session : SESSION_MAP_BY_ID.values()) {
			try {
				result += now - session.getCreationTime();
			} catch (final Exception e) {
				// Tomcat can throw "java.lang.IllegalStateException: getCreationTime: Session already invalidated"
				continue;
			}
		}
		return result;
	}
@Test
	public void testGetSessionAgeSum() {
		sessionListener.sessionCreated(createSessionEvent());
		if (SessionListener.getSessionAgeSum() < 0) {
			fail("getSessionAgeSum");
		}
	}