public synchronized void cleanRemovedTasks(final long cleanupDelayMs) {
        try {
            cleanRemovedTasksCalledByCleanerThread(cleanupDelayMs);
        } catch (final Exception cannotHappen) {
            throw new IllegalStateException("Should have swallowed exception.", cannotHappen);
        }
    }
@Test
    public void shouldNotRemoveNonTaskDirectoriesAndFiles() {
        final File otherDir = TestUtils.tempDirectory(stateDir.toPath(), "foo");
        directory.cleanRemovedTasks(0);
        assertTrue(otherDir.exists());
    }