public static Builder builder() {
    return new Builder(ImmutableList.of());
  }
@Test
  public void shouldThrowOnDuplicateKeyColumnName() {
    // Given:
    final Builder builder = LogicalSchema.builder()
        .keyColumn(KEY, BIGINT);

    // When:
    final Exception e = assertThrows(
        KsqlException.class,
        () -> builder.keyColumn(KEY, BIGINT)
    );

    // Then:
    assertThat(e.getMessage(), containsString("Duplicate key columns found in schema: `key` BIGINT"));
  }