The ABACABA sequence

the-abacaba-sequence.ps1

# Author: Jakub Šindelář megastary@houby-studio.eu
# Date: 2021-06-28

# Solution definition
function abacaba {
  [CmdletBinding()]
  param (
    [Parameter()]
    [String]
    $CurrentSequence = '',
    [Parameter()]
    [Int32]
    $CurrentLoopIndex = 0
  )
  $CurrentLetter = [char](65 + $CurrentLoopIndex)
  $CurrentSequence = $CurrentSequence + $CurrentLetter + $CurrentSequence
  $CurrentLoopIndex++
  if ($CurrentLoopIndex -eq 26) {
    $CurrentSequence
  }
  else {
    abacaba -CurrentSequence $CurrentSequence -CurrentLoopIndex $CurrentLoopIndex
  }
}

the-abacaba-sequence.Tests.ps1

# Test result with Pester
# Install with: Install-Module Pester -MinimumVersion 4.0.0 -Force -SkipPublisherCheck

# Import tested script
BeforeAll { 
  . $PSCommandPath.Replace('.Tests.ps1', '.ps1')
  $File = "$([IO.Path]::GetTempPath())/$([Guid]::NewGuid())abacaba.txt"
  New-Item -Path $File
}

Describe 'abacaba' {
  Context 'no parameters' {
    It 'resulting length is 67,108,863 characters' {
      $abacaba = abacaba
      $abacaba.Length | Should -Be 67108863
    }
    It 'resulting file size is 64MB' {
      abacaba | Out-File -FilePath $File
      [Int32]((Get-Item -Path $File).Length / 1MB) | Should -Be 64
    }
  }
}

AfterAll {
  if (Test-Path $File) {
    Remove-Item -Path $File
  }
}

This gist is my PowerShell solution to challenge https://old.reddit.com/r/dailyprogrammer/comments/njxq95/20210524_challenge_391_easy_the_abacaba_sequence/