public function test_regression( $lang, $nplurals, $expression ) {
    require_once dirname( dirname( __DIR__ ) ) . '/includes/plural-form-function.php';

    $parenthesized = self::parenthesize_plural_expression( $expression );
    $old_style     = tests_make_plural_form_function( $nplurals, $parenthesized );
    $plural_forms  = new Plural_Forms( $expression );

    $generated_old = array();
    $generated_new = array();

    foreach ( range( 0, 200 ) as $i ) {
      $generated_old[] = $old_style( $i );
      $generated_new[] = $plural_forms->get( $i );
    }

    $this->assertSame( $generated_old, $generated_new );
  }