public function test_validate_date_values_month() {
    // Valid values.
    $months = range( 1, 12 );
    foreach ( $months as $month ) {
      $this->assertTrue( $this->q->validate_date_values( array( 'month' => $month ) ) );
    }

    // Invalid values.
    $months = array( -1, 0, 13, 'string who wants to be a int' );
    foreach ( $months as $month ) {
      $this->assertFalse( $this->q->validate_date_values( array( 'month' => $month ) ) );
    }
  }