Add folder to zip - powershell

Question

I am facing a problem how to add folder to existing ZIP file.
This zip file is created by PowerShell also.
I can only use system classes provided by Powershell 5. I cannot use any of user packages or plugins (7zip included).
Here is my code:
function addFileToArchiveTest ($filePathToAdd, $archivePathToUpdate) {
if ([System.IO.File]::Exists($filePathToAdd) -or (Test-Path $filePathToAdd)) {
$file = [System.IO.Path]::GetFileName($filePathToAdd);
Write-Host $filePathToAdd.Name;
Write-Host $filePathToAdd;
Write-Host $archivePathToUpdate;
$archive = [System.IO.Compression.ZipFile]::Open($archivePathToUpdate, [System.IO.Compression.ZipArchiveMode]::Update);
$compressionLevel = [System.IO.Compression.CompressionLevel]::NoCompression;
[System.IO.Compression.ZipFileExtensions]::CreateEntryFromFile($archive, $filePathToAdd, $file, "$compressionLevel");
$archive.Dispose();
} else {
Write-Host "[ERROR#function] <AddFileToArchive>: <filePathToAdd> does not exist!";
Write-Host "[ERROR#function] <Variable<filePathToAdd>>: $filePathToAdd";
Write-Host "[ERROR#function] <Variable<archivePathToUpdate>>: $archivePathToUpdate";
}
}
I am thinking about variable $file - there might be a problem, because folder doesn't have an extension.
I run script like this:
PS> addFileToArchiveTest "C:\TestFolder\FolderToArchive" "C:\TestFolder\thereIsAlreadyZipFile.zip"
It returns with error:
Exception calling "CreateEntryFromFile" with "4" argument(s): "Access to the
path 'C:\TestFolder\FolderToArchive' is denied."
At C:\Users\user\Desktop\testfolder.ps1:196 char:13
+ [System.IO.Compression.ZipFileExtensions]::CreateEntryFro ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : UnauthorizedAccessException
Noted I also try allow script and I am launching with admin rights.

Answer 1

Perhaps surprisingly, CreateEntryFromFile() is for adding files, not folders. You need to add each file individually:
Get-ChildItem $filePathToAdd | ForEach-Object {
[IO.Compression.ZipFileExtensions]::CreateEntryFromFile($archive, $_.FullName, $_.Name, "$compressionLevel")
}

Answer 2

As user #guiwhatsthat answered: PowerShell 5 does support Compress-Archive. It does exactly what you want.
That is working as I want.