@Override
    public void deleteTarget(final Target target) {
        final long streamId = target.getMeta().getId();
        openOutputStream.remove(streamId);
        fileData.remove(streamId);
        ((MockTarget) target).delete();
    }
Class this API to clear down things.
stroom-data/stroom-data-store-mock/src/main/java/stroom/data/store/mock/MockStore.java