Operator to test sort order for Pester.

SortOrderAssertOperation.ps1

Import-Module Pester -MinimumVersion 4.0.5 -Force

<#
.EXAMPLE
  It "Hoge" {
    $collection | Should -BeSorted Field1,...
  }
#>
function BeSorted($ActualValue, [string[]]$SortFields, [switch]$Negate, [int]$Sample = -1) {
  $values = 
    if ($Sample -gt 0) {
      $ActualValue | select -Property $SortFields -First $Sample
    }
    else {
      $ActualValue | select -Property $SortFields
    }
    
  $sortedKeys =
    $values |
    %{$seq = 0}{ $_ | Add-Member NoteProperty BeforeIndex $seq -PassThru; ++$seq } |
    sort -Property ($SortFields + @("BeforeIndex")) -CaseSensitive |
    %{$seq1 = 0}{ $_ | Add-Member NoteProperty AfterIndex $seq1 -PassThru; ++$seq1 } 
  
  [bool]$failure = 
    if (-Not $Negate) {
      $sortedKeys | ?{ $_.BeforeIndex -ne $_.AfterIndex }
    }
    else {
      $sortedKeys | ?{ $_.BeforeIndex -eq $_.AfterIndex }
    }
  
  $message = $sortedKeys | select -First 1 | %{ "Incorrect sort order: [$(_FormatFalureMessage $_ $SortFields) (Index: $($_.BeforeIndex) => $($_.AfterIndex)) ...]" }
  
  [PSCustomObject]@{
    Succeeded = -Not $failure
    FailureMessage  = $message
  }
}

function _FormatFalureMessage($obj, [string[]]$names) {
  $messages = 
    foreach ($n in $names) {
      '{0} = `{1}`' -F $n,$obj."$n"
    }
    
  $messages -join ", "
}

Add-AssertionOperator -Name BeSorted -Test $function:BeSorted -SupportsArrayInput