adapt test_update_cycle powershell script to work on macos as well

(tested on windows but not yet on macos...)

test_update_cycle.ps1

@@ -24,6 +24,8 @@
 # but workflow failures are easier to debug when broken down into
 # separate steps
 
+# requires Powershell 6 or higher
+
 # exit on cmdlet errors
 $ErrorActionPreference = "stop"
 
@@ -41,11 +43,21 @@ $enable_patch_update = $true
 
 # directories where this script creates files and deletes files (note these must end
 # with $app_name and must be consistent with myapp.settings and repo_settings)
-$repo_dir = $PSScriptRoot
-$temp_dir = "$repo_dir\temp_$app_name"
-$app_install_dir = "$env:LOCALAPPDATA\Programs\$app_name"
-$app_data_dir = "$env:LOCALAPPDATA\$app_name"
-$targets_dir = "$app_data_dir\update_cache\targets"
+$repo_dir = "$PSScriptRoot"
+$temp_dir = Join-Path "$repo_dir" "temp_$app_name"
+if ( $IsWindows ) {
+    $app_install_dir = Join-Path "$env:LOCALAPPDATA" "Programs" "$app_name"
+    $app_data_dir = Join-Path "$env:LOCALAPPDATA" "$app_name"
+    $path_separator = ";"
+} elseif ( $IsMacOS ) {
+    $app_install_dir = Join-Path "$HOME" "Applications" "$app_name"
+    $app_data_dir = Join-Path "$HOME" "Library" "$app_name"
+    $path_separator = ":"
+} else {
+    Write-Host "unsupported OS" -ForegroundColor red
+    exit 1
+}
+$targets_dir = Join-Path "$app_data_dir" "update_cache" "targets"
 $all_app_dirs = @($temp_dir, $app_install_dir, $app_data_dir)
 
 function Remove-MyAppDirectory {
@@ -68,7 +80,7 @@ function Remove-MyApp {
 }
 
 function Invoke-PyInstaller {
-    pyinstaller.exe "$repo_dir\main.spec" --clean -y --distpath "$temp_dir\dist" --workpath "$temp_dir\build"
+    pyinstaller "$repo_dir/main.spec" --clean -y --distpath "$temp_dir/dist" --workpath "$temp_dir/build"
     Assert-ExeSuccess
 }
 
@@ -86,7 +98,7 @@ New-Item -Path $targets_dir -ItemType "directory" -Force | Out-Null
 
 # this script requires an active python environment, with tufup installed
 # (we'll assume there's a venv in the repo_dir)
-$venv_path = "$repo_dir\venv\Scripts\activate.ps1"
+$venv_path = Join-Path "$repo_dir" "venv" "Scripts" "activate.ps1"
 if (Test-Path $venv_path) {
     & $venv_path
     Write-Host "venv activated" -ForegroundColor green
@@ -95,11 +107,11 @@ if (Test-Path $venv_path) {
 }
 
 # make sure python can find myapp
-$Env:PYTHONPATH += ";$repo_dir\src"
+$Env:PYTHONPATH += "$path_separator$repo_dir/src"
 
 # - initialize new repository
 Write-Host "initializing tuf repository for $app_name" -ForegroundColor green
-python "$repo_dir\repo_init.py"
+python "$repo_dir/repo_init.py"
 Assert-ExeSuccess
 
 # - create my_app v1.0 bundle using pyinstaller
@@ -108,12 +120,12 @@ Invoke-PyInstaller
 
 # - add my_app v1.0 to tufup repository
 Write-Host "adding $app_name v1.0 bundle to repo" -ForegroundColor green
-python "$repo_dir\repo_add_bundle.py"
+python "$repo_dir/repo_add_bundle.py"
 Assert-ExeSuccess
 
 # - mock install my_app v1.0
 Write-Host "installing $app_name v1.0 in $app_install_dir" -ForegroundColor green
-$myapp_v1_archive = "$temp_dir\repository\targets\$app_name-1.0.tar.gz"
+$myapp_v1_archive = Join-Path "$temp_dir" "repository" "targets" "$app_name-1.0.tar.gz"
 tar -xf $myapp_v1_archive --directory=$app_install_dir
 # put a copy of the archive in the targets dir, to enable patch updates
 if ($enable_patch_update) {
@@ -125,7 +137,7 @@ if ($enable_patch_update) {
 # (quick and dirty, this modifies the actual source,
 # but the change is rolled back later...)
 Write-Host "bumping $app_name version to v2.0 (temporary)" -ForegroundColor green
-$settings_path = "$repo_dir\src\myapp\settings.py"
+$settings_path = Join-Path "$repo_dir" "src" "myapp" "settings.py"
 (Get-Content $settings_path).Replace("1.0", "2.0") | Set-Content $settings_path
 
 # - create my_app v2.0 bundle using pyinstaller
@@ -134,7 +146,7 @@ Invoke-PyInstaller
 
 # - add my_app v2.0 to tufup repository
 Write-Host "adding $app_name v2.0 bundle to repo" -ForegroundColor green
-python "$repo_dir\repo_add_bundle.py"
+python "$repo_dir/repo_add_bundle.py"
 Assert-ExeSuccess
 
 # - roll-back modified source
@@ -143,7 +155,7 @@ Write-Host "rolling back temporary source modification" -ForegroundColor green
 
 # - start update server
 Write-Host "starting update server" -ForegroundColor green
-$job = Start-Job -ArgumentList @("$temp_dir\repository") -ScriptBlock {
+$job = Start-Job -ArgumentList @("$temp_dir/repository") -ScriptBlock {
     param($repository_path)
     python -m http.server -d $repository_path
     Assert-ExeSuccess
@@ -152,14 +164,16 @@ sleep 1  # not sure if this is required, but cannot hurt
 
 # - run my_app to update from v1 to v2
 Write-Host "running $app_name for update..." -ForegroundColor green
-Invoke-Expression "$app_install_dir\main.exe"
+& "$app_install_dir\main"
 Assert-ExeSuccess
 
 # - run my_app again to verify we now have v2.0
 Write-Host "hit enter to proceed, after console has closed:"  -ForegroundColor yellow -NoNewLine
 Read-Host  # no text: we use write host to add color
 Write-Host "running $app_name again to verify version" -ForegroundColor green
-$output = Invoke-Expression "$app_install_dir\main.exe"
+# https://devblogs.microsoft.com/powershell/invoke-expression-considered-harmful/
+# https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_operators?view=powershell-7.4#call-operator-
+$output = & "$app_install_dir/main"
 Assert-ExeSuccess
 
 # - stop update server