1. Unit Testing
PowerShell
Matt Wrock (@mwrockx)
April 22 – 24
Microsoft campus
Redmond

2. Describe "Invoke-Reboot" {
Context "When reboots are suppressed" {
Mock New-Item -parameterFilter {$Path -like "*Boxstarter*"}
Mock Restart
$Boxstarter.RebootOk=$false
$Boxstarter.IsRebooting=$false
Invoke-Reboot
it "will not create Restart file" {
Assert-MockCalled New-Item -times 0
}
it "will not restart" {
Assert-MockCalled Restart -times 0
}
it "will not toggle reboot" {
$Boxstarter.IsRebooting | should be $false
}
}
}
A PowerShell Unit Test in the
wild
I’m all about test coverage
Executing all tests in C:devboxstartertestsInvoke-Reboot.tests.ps1
Describing Invoke-Reboot
When reboots are suppressed
[+] will not create Restart file 6ms
[+] will not restart 11ms
[+] will not toggle reboot 4ms
When reboots are not suppressed
[+] will create Restart file 11ms
[+] will restart 5ms
[+] will toggle reboot 2ms
Tests completed in 41ms
Passed: 6 Failed: 0

3. Why Test PowerShell?
Do NOT UnitTest your scripts if
you like surprises!
• Your scripts will likely be
easier to understand
• Catch regressions
• How does your API really
feel?

4. Managed Unit Testing Tools vs.
PowerShell
Managed
• Xunit - https://xunit.codeplex.com/
• Nunit - http://www.nunit.org/
• MSTest
PowerShell
• Pester - https://github.com/pester/Pester
• PSUnit - http://psunit.org/
• PSTest - https://github.com/knutkj/pstest/wiki
If practical, test powershell code in PowerShell:
• Saves the overhead of starting a runspace for each test
• Environment more closely resembles the user’s

5. PowerShell Unit Testing
Patterns

6. Abstracting the untestableFunction Under Test
function Install-ChocolateyVsixPackage {
$installer = Join-Path $env:VS110COMNTOOLS "..IDEVsixInstaller.exe"
$download="MyVSIX.vsix"
Write-Debug "Installing VSIX using $installer"
$exitCode = Install-Vsix "$installer" "$download"
if($exitCode -gt 0 -and $exitCode -ne 1001) { #1001: Already installed
Write-ChocolateyFailure "There was an error installing."
return
}
Write-ChocolateySuccess
}
Wrap the EXE
function Install-Vsix($installer, $installFile) {
Write-Host "Installing $installFile using $installer"
$psi = New-Object System.Diagnostics.ProcessStartInfo
$psi.FileName=$installer
$psi.Arguments="/q $installFile"
$s = [System.Diagnostics.Process]::Start($psi)
$s.WaitForExit()
return $s.ExitCode
}
Test and Mock the Wrapper
Context "When VSIX is already installed" {
Mock Install-Vsix {return 1001}
Install-ChocolateyVsixPackage
It "should succeed" {
Assert-MockCalled Write-ChocolateySuccess
}
}

7. Mocking Cmdletsfunction Get-LatestVSVersion {
$versions=(
get-ChildItem HKLM:SOFTWAREWow6432NodeMicrosoftVisualStudio `
-ErrorAction SilentlyContinue | ? {
($_.PSChildName -match "^[0-9.]+$")
} | ? {
$_.property -contains "InstallDir"
} | sort {[int]($_.PSChildName)} -descending
)
if($versions -and $versions.Length){
$version = $versions[0]
}elseif($versions){
$version = $versions
}
return $version
}
Context "When version 9, 10 and 11 is installed" {
Mock Get-ChildItem {@(
@{PSChildName="9.0";Property=@("InstallDir");PSPath="9"},
@{PSChildName="10.0";Property=@("InstallDir");PSPath="10"},
@{PSChildName="11.0";Property=@("InstallDir");PSPath="11"}
)} `
-parameterFilter {
$path -eq "HKLM:SOFTWAREWow6432NodeMicrosoftVisualStudio"
}
Mock get-itemproperty {@{InstallDir=$Path}}
$result=Get-LatestVSVersion
It "should return version 11" {
$result | Should Be 11
}
}

8. Isolating file operationsfunction Set-BoxstarterShare {
param(
[string]$shareName="Boxstarter",
[string[]]$accounts=@("Everyone")
)
foreach($account in $accounts){
$acctOption += "/GRANT:'$account,READ' "
}
IEX "net share $shareName='$($Boxstarter.BaseDir)' $acctOption"
if($LastExitCode -ne 0) {
Throw "Share was not succesfull."
}
}
Describe "Set-BoxstarterShare" {
$testRoot=(Get-PSDrive TestDrive).Root
Context "When setting share with no parameters" {
MkDir "$testRootboxstarter" | Out-Null
$Boxstarter.BaseDir="$testRootBoxstarter"
Set-BoxstarterShare
It "Should create Boxstarter Share"{
Test-Path "$env:ComputernameBoxstarter" | should be $true
}
It "Should give read access to everyone"{
(net share Boxstarter) | ? { $_.StartsWith("Permission")} | % {
$_.ToLower().EndsWith("everyone, read") | Should be $true
}
}
net share Boxstarter /delete
}
}
Using the Pester TestDrive:

9. Testing Exceptionsfunction Set-BoxstarterShare {
param(
[string]$shareName="Boxstarter",
[string[]]$accounts=@("Everyone")
)
foreach($account in $accounts){
$acctOption += "/GRANT:'$account,READ' "
}
IEX "net share $shareName='$($Boxstarter.BaseDir)' $acctOption"
if($LastExitCode -ne 0) {
Throw "Share was not succesfull."
}
}
Context "When share already exists" {
MkDir "$testRootboxstarter" | Out-Null
$Boxstarter.BaseDir="$testRootBoxstarter"
Net share Boxstarter="$($Boxstarter.BaseDir)"
try {Set-BoxstarterShare} catch{$ex=$_}
It "Should throw exception"{
$ex | should not be $null
}
net share Boxstarter /delete
}

10. Debugging Tests
Doug Finke’s IsePester
https://github.com/dfinke/IsePester
Chocolatey (downloads pester,
isepester and imports them in your
ISE profile):
cinst IsePester
Ctrl+F5
Debugs tests in the active editor

11. A PowerShell CI Build
<Project ToolsVersion="4.0“ DefaultTargets="Go“ xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<GoDependsOn>Tests</GoDependsOn>
<Configuration>Release</Configuration>
<Platform>Any CPU</Platform>
</PropertyGroup>
<Target Name="Go" DependsOnTargets="$(GoDependsOn)" />
<Target Name="Tests">
<Exec Command="cmd /c $(MSBuildProjectDirectory)pesterbinpester.bat" />
</Target>
</Project>
Simple MSBuild script
A better way: Psake
https://github.com/psake/psake
$psake.use_exit_on_error = $true
properties {
$baseDir = (Split-Path -parent $psake.build_script_dir)
}
Task default -depends Test
Task Test {
pushd "$baseDir"
$pesterDir = (dir $env:ChocolateyInstalllibPester*)
if($pesterDir.length -gt 0) {$pesterDir = $pesterDir[-1]}
exec {."$pesterDirtoolsbinPester.bat" $baseDir/Tests }
popd
}

12. A PowerShell CI Build
Adding test detail to TeamCity builds:
https://github.com/pester/Pester/wiki/Showing-Test-Results-in-TeamCity

13. PowerShell Unit Test Samples
• Chocolatey
https://github.com/chocolatey/chocolatey/tree/master/tests
• Pester
https://github.com/pester/Pester/tree/master/Functions
• Boxstarter
http://boxstarter.codeplex.com/