code: void clear() {
      try (Connection conn = datasource.getConnection()) {
        context.get(conn).truncate(ZIPKIN_SPANS).execute();
        context.get(conn).truncate(ZIPKIN_ANNOTATIONS).execute();
        context.get(conn).truncate(ZIPKIN_DEPENDENCIES).execute();
      } catch (SQLException | RuntimeException e) {
        throw new AssertionError(e);
      }
    }
docs: Visible for testing