new_contents: # Copyright 2021 ScyllaDB
  #
  # This file is part of Scylla.
  #
  # Scylla is free software: you can redistribute it and/or modify
  # it under the terms of the GNU Affero General Public License as published by
  # the Free Software Foundation, either version 3 of the License, or
  # (at your option) any later version.
  #
  # Scylla is distributed in the hope that it will be useful,
  # but WITHOUT ANY WARRANTY; without even the implied warranty of
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  # GNU General Public License for more details.
  #
  # You should have received a copy of the GNU Affero General Public License
  # along with Scylla.  If not, see <http://www.gnu.org/licenses/>.
  
  from cassandra.cluster import ConsistencyLevel
  from cassandra.query import SimpleStatement
  
  from util import new_test_table
  
  def test_cdc_log_entries_use_cdc_streams(cql, test_keyspace):
      '''Test that the stream IDs chosen for CDC log entries come from the CDC generation
      whose streams are listed in the streams description table. Since this test is executed
      on a single-node cluster, there is only one generation.'''
  
      schema = "pk int primary key"
      extra = " with cdc = {'enabled': true}"
      with new_test_table(cql, test_keyspace, schema, extra) as table:
          stmt = cql.prepare(f"insert into {table} (pk) values (?) using timeout 5m")
          for i in range(100):
              cql.execute(stmt, [i])
  
          log_stream_ids = set(r[0] for r in cql.execute(f'select "cdc$stream_id" from {table}_scylla_cdc_log'))
  
      # There should be exactly one generation, so we just select the streams
      streams_desc = cql.execute(SimpleStatement(
              'select streams from system_distributed.cdc_streams_descriptions_v2',
              consistency_level=ConsistencyLevel.ONE))
      stream_ids = set()
      for entry in streams_desc:
          stream_ids.update(entry.streams)
  
      assert(log_stream_ids.issubset(stream_ids))
  
  
subject: add a simple CDC cql pytest