How can I create a DSL similar to Pester in PowerShell? - powershell

Question

The Vester project creates pester tests that follow a specific pattern of Describe, It, Try, Catch, Remdiate to test and then fix issues with a VMWare environment, Ex. Update-DNS.Tests.ps1.
In semi-pseudo code, the core of the algorithm is the following:
Param(
[switch]$Remediate = $false
)
Process {
Describe -Name "Test Group Name" -Tag #("Tag") -Fixture {
#Some code to load up state for the test group
foreach ($Thing in $Things) {
It -name "Name of first test" -test {
#Some code to load up state for the test
try {
#Conditional tests using Pester syntax
} catch {
if ($Remediate) {
Write-Warning -Message $_
Write-Warning -Message "Remediation Message"
#Code to remediate issues
} else {
throw $_
}
}
}
}
}
}
I would like to be able to write the code that would allow for the following Pester like DSL syntax:
Param(
[switch]$Remediate = $false
)
CheckGroup "AD User Checks" {
ForEach($Aduser in (Get-aduser -Filter * -Properties HomeDirectory)) {
Check "Home directory path exists" {
Condition {
if ($Aduser.HomeDirectory) {
Test-path $Aduser.HomeDirectory | Should be $true
}
}
Remdiation "Create home directory that doesn't exist" {
New-Item -ItemType Directory -Path $Aduser.HomeDirectory
}
}
}
}
Running this would result in something like the following actually being run:
Describe -Name "AD User Checks" -Fixture {
ForEach($Aduser in (Get-aduser -Filter * -Properties HomeDirectory)) {
It -name "Home directory path exists" -test {
try {
if ($Aduser.HomeDirectory) {
Test-path $Aduser.HomeDirectory | Should be $true
}
} catch {
if ($Remediate) {
Write-Warning -Message $_
Write-Warning -Message "Create home directory that doesn't exist"
New-Item -ItemType Directory -Path $Aduser.HomeDirectory
} else {
throw $_
}
}
}
}
}
How can I go about implementing this DSL designed specifically for performing checks and remediations?
Here is some of the code that I have written to try to accomplish this:
Function CheckGroup {
param (
[Parameter(Mandatory, Position = 0)][String]$Name,
[Parameter(Position = 1)]$CheckGroupScriptBlock
)
Describe $CheckGroupName -Fixture $CheckGroupScriptBlock
}
Function Check {
param (
[Parameter(Mandatory, Position = 0)][String]$Name,
$ConditionScriptBlock,
$RemediationScriptBlock
)
It -name $Name -test {
try {
& $ConditionScriptBlock
} catch {
& $RemediationScriptBlock
}
}
}
Function Condition {
[CmdletBinding()]
param (
[Parameter(Position = 1)]$ScriptBlock
)
& $ScriptBlock
}
Function Remediation {
[CmdletBinding()]
param (
$Name,
[Parameter(Position = 1)]$ScriptBlock,
[bool]$Remediate = $false
)
if ($Remediate) {
Write-Verbose $_
Write-Verbose $Name
& $ScriptBlock
} else {
throw $_
}
}
For the function Check I really need to be able to take in a single script block as a parameter but somehow find the Condition and Remediation function calls inside the script block passed and split them out of the script block and blend them into the appropriate spot in the Try {} Catch {} inside the It in the Check function.