trait SchemaIntrospectionTestTrait in Drupal 8

trait SchemaIntrospectionTestTrait {

  /**
   * Checks that an index covering exactly the given column names exists.
   *
   * @param string $table_name
   *   A non-prefixed table name.
   * @param array $column_names
   *   An array of column names
   * @param string $index_type
   *   (optional) The type of the index. Can be one of 'index', 'unique' or
   *   'primary'. Defaults to 'index'.
   */
  protected function assertIndexOnColumns($table_name, array $column_names, $index_type = 'index') {
    foreach ($this
      ->getIndexColumnNames($table_name, $index_type) as $index_columns) {
      if ($column_names == $index_columns) {
        $this
          ->assertTrue(TRUE);
        return;
      }
    }
    $this
      ->assertTrue(FALSE);
  }

  /**
   * Checks that an index covering exactly the given column names doesn't exist.
   *
   * @param string $table_name
   *   A non-prefixed table name.
   * @param array $column_names
   *   An array of column names
   * @param string $index_type
   *   (optional) The type of the index. Can be one of 'index', 'unique' or
   *   'primary'. Defaults to 'index'.
   */
  protected function assertNoIndexOnColumns($table_name, array $column_names, $index_type = 'index') {
    foreach ($this
      ->getIndexColumnNames($table_name, $index_type) as $index_columns) {
      if ($column_names == $index_columns) {
        $this
          ->assertTrue(FALSE);
      }
    }
    $this
      ->assertTrue(TRUE);
  }

  /**
   * Returns the column names used by the indexes of a table.
   *
   * @param string $table_name
   *   A table name.
   * @param string $index_type
   *   The type of the index. Can be one of 'index', 'unique' or 'primary'.
   *
   * @return array
   *   A multi-dimensional array containing the column names for each index of
   *   the given type.
   */
  protected function getIndexColumnNames($table_name, $index_type) {
    assert(in_array($index_type, [
      'index',
      'unique',
      'primary',
    ], TRUE));
    $schema = \Drupal::database()
      ->schema();
    $introspect_index_schema = new \ReflectionMethod(get_class($schema), 'introspectIndexSchema');
    $introspect_index_schema
      ->setAccessible(TRUE);
    $index_schema = $introspect_index_schema
      ->invoke($schema, $table_name);

    // Filter the indexes by type.
    if ($index_type === 'primary') {
      $indexes = [
        $index_schema['primary key'],
      ];
    }
    elseif ($index_type === 'unique') {
      $indexes = array_values($index_schema['unique keys']);
    }
    else {
      $indexes = array_values($index_schema['indexes']);
    }
    return $indexes;
  }

}