Validate checkboxes with CF7 | WordPress.org

How? Validate checkboxes with CF7

I have this code

function cf7_length_validation_filter( $result, $tag ) {
	$name = $tag['name'];
	$value = isset( $_POST[$name] ) ? trim( $_POST[$name] ) : '';
	$minLen = 0;
	
	// Empty Fields
	if( empty( $value ) || strlen( $value ) == 0 ) {
		$result->invalidate( $tag, "Field cannot be empty." );
	}
	
	// Field Length
	switch ( $name ) {
		case 'fname':
		case 'lname':
			$minLen = 2;
			break;
		case 'email':
			$minLen = 6;
			break;
	}
	
	if ( empty( $value ) || strlen( $value ) < $minLen ) {
		$result->invalidate( $tag, "This field is too short." );
	}


	return $result;
}

It works for those fields. For checkbox, it ALWAYS says This field is too short

add_filter( ‘wpcf7_validate_checkbox*’, ‘cf7_length_validation_filter’, 5, 2 );

without this line, no validation happens at all