Powershell missing int parameter detection

foo.ps1

function testnull {
    param([System.Nullable[int]] $testint)
    if($testint){
        Write-Host "Value was found to be null implicitly"
    } else {
        Write-Host "Value was found to not be null implicitly"
    }
    if($testint -eq $null){
        Write-Host "Value was found to be null by explicit null comparison"
    } else {
        Write-Host "Value was found to not be null by explicit null comparison"
    }
    if(($testint -eq $null) -and ($testint -ne 0)){
        Write-Host "Value was found to be null by explicit compound null comparison"
    } else {
        Write-Host "Value was found to not be null by explicit compound null comparison"
    }
    Write-Host "Value was found to be `"$testint`""

    return
}

Clear-Host
Write-Host "Missing Param case"
testnull 
Start-Sleep -Seconds 2 | Out-Null
Write-Host "Zero value case"
testnull -testint 0
Start-Sleep -Seconds 2 | Out-Null
Write-Host "Non-zero value case"
testnull -testint 2

Missing Param case
Value was found to not be null implicitly
Value was found to be null by explicit null comparison
Value was found to be null by explicit compound null comparison
Value was found to be ""
Zero value case
Value was found to not be null implicitly
Value was found to not be null by explicit null comparison
Value was found to not be null by explicit compound null comparison
Value was found to be "0"
Non-zero value case
Value was found to be null implicitly
Value was found to not be null by explicit null comparison
Value was found to not be null by explicit compound null comparison
Value was found to be "2"