Mandatory user provided parameter in PowerShell

function-mandatoryUserBoolParam.ps1

function mandatoryUserBoolParam {
    param(
        [Parameter(Mandatory=$true)]
        [ValidateSet("true","false","1","0","yes","no","y","n")]
        [string]$param
    )
    $boolParam = $false
    switch ($param.ToLower()) {
        "true" { $boolParam = $true }
        "1" { $boolParam = $true }
        "yes" { $boolParam = $true }
        "y" { $boolParam = $true }
        default { $boolParam = $false }
    }
    $boolParam
}

class SwitchTransformAttribute : System.Management.Automation.ArgumentTransformationAttribute {
 [object] Transform([System.Management.Automation.EngineIntrinsics]$EngineIntrinsics, [object]$Object) {
    if ($Object -is [bool]) { return [bool]$object }
    if ("$Object".ToLower() -in "yes","true",'$true',"1","y") { return $true }
    if ("$Object".ToLower() -in "no","false",'$false',"0","n") { return $false }
    
    # if you wanted to _never_ have a conversion failure, you could just:
    # return [bool]$object
    # But this way, if they just mash the keyboard, "asdf" won't be treated as $true
    return $object
 }
}

function Test-Switch {
  [CmdletBinding()]
  param(
    [Parameter(Mandatory)]
    [SwitchTransform()]
    [switch]
    $Seriously
  )
  $Seriously.IsPresent 
}