public KsqlTopic getPrimarySourceTopic() {
    return primarySourceTopic;
  }
@Test
  public void shouldExtractPrimaryTopicFromJoinSelect() {
    // Given:
    final Statement statement = givenStatement(String.format(
        "SELECT * FROM %s A JOIN %s B ON A.F1 = B.F1;", STREAM_TOPIC_1, STREAM_TOPIC_2
    ));

    // When:
    extractor.process(statement, null);

    // Then:
    assertThat(extractor.getPrimarySourceTopic(), is(TOPIC_1));
  }