ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.

[DkSkydancer]

Hi

I am converting a data-driven test from Pester 4 to 5. It verifies that files produced by my script has none of the known tokens present in their content. My test worked in Pester 4, but now I can't get them to work. The test fails with a series of "ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null." - one error per token I'm looking for.

The problem seems to be about the test script input parameter ($TestRoot), which I pass in from the test harness and its used to pass to teh -Path property of Get-ChildItem. What's "funny" is my test harness actually runs to test scripts and one works (pass TestRoot as data) the other fails. And I verify in both scripts via "BeforeDiscovery" that TestRoot has a value - its output twice successfully in the console window. The failing one is the data driven test.

I am hoping someone can spot the problem, because i have not been successful so far: but I wonder from the error message if "Path" is not about what is passed to Get-ChildItem -Path $TestRoot but maybe it's about some other parameter binding that i am not aware of is going on?

Test file that fails:

#Requires -Version 7.1

[CmdletBinding()]
param(
  [string]$TestRoot
)

BeforeDiscovery {
  Write-Host "Directory for discovery: $($TestRoot)"
}

Describe 'Verifying that all tokens have been replaced in all generated files' {
  $allFiles = Get-ChildItem -Path $TestRoot -Include '*.*' -Recurse -File
  $tokens = @('TeamNameToken', 'MicroserviceNameToken', 'ServiceTreeIdToken', 'AreaPathToken', 'AadAppIdToken', 'AadObjectIdToken', 'AadTenantIdToken', 'RolloutSpecEmailAliasToken', 'IcmPathToken', 'MdmAccountToken', 'MdmNamespaceToken', 'MicroserviceNameTokenLower')
  Describe '"Finding leftover tokens in <fullName>"' -ForEach $allFiles {
    Describe 'should not contain the token <token>' -ForEach $tokens {
      BeforeAll {
        # Renaming the automatic $_ variable to $token to make it easier to work with
        $token = $_
      }
      It 'No files Should contain unreplaced tokens' {
          $fullName | Should -Not -FileContentMatch $token
      }
    }
  }
}

Test file that succeeds:

#Requires -Version 7.1

[CmdletBinding()]
param(
  [string]$TestRoot
)

BeforeDiscovery {
  Write-Host "Directory for discovery: $($TestRoot)"
}

Describe 'Verify all .tpl files have been renamed' {
  It 'Should no longer exist ' {
    $templateFileCount = @(Get-ChildItem -File -Recurse -Path $TestRoot -Include '*.tpl').Length 
    $templateFileCount | Should -Be 0
  }
}

Test harness (execution):

              $PesterVersion = "5.5.0"

              Write-Output 'Restoring Pester from Central Feed service'
              Register-PackageSource -Name PowerPlatform-Microservices-Package-In -ProviderName NuGet -Location "https://msazure.pkgs.visualstudio.com/One/_packaging/PowerPlatform-Microservices-Package-In/nuget/v3/index.json" -Trusted -ErrorAction SilentlyContinue
              Install-Module -Name Pester -Force 

              Write-Host "Importing Pester"
              Import-Module -Name Pester -RequiredVersion $PesterVersion -PassThru

              # container is used to include the parameters to pass into the Pester file
              $container = New-PesterContainer -Verbose -Path ".\NewRepopo.*.Tests.ps1" -Data @{ 
                  TestRoot = "c:\temp\test"; 
              }

              Write-Host "Changing PesterConfiguration"
              
              # create a new configuration with our settings
              $config = New-PesterConfiguration
              $config.Output.Verbosity = "Detailed" # D"Diagnostic"
              $config.TestResult.OutputFormat = "NUnitXML"
              $config.TestResult.OutputPath = ".\out\Validate-Pester.xml"
              $config.TestResult.Enabled = $true
              $config.Should.ErrorAction = 'Continue'

              # configure the run with the new container
              $config.Run.Container = $container

              Write-Host "Running Pester."
              Invoke-Pester -Configuration $config

Output:

Running tests from 'D:\Repos\msazure-finops\ENG-RepositoryTemplate\src\TemplatingTool\TemplateTests\foislandsrepo\NewRepopo.Token.Tests.ps1'
Describing Verifying that all tokens have been replaced in all generated files
 Describing "Finding leftover tokens in "
  Describing should not contain the token TeamNameToken
    [-] No files Should contain unreplaced tokens 10ms (4ms|6ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.
  Describing should not contain the token MicroserviceNameToken
    [-] No files Should contain unreplaced tokens 11ms (9ms|2ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.
  Describing should not contain the token ServiceTreeIdToken
    [-] No files Should contain unreplaced tokens 6ms (3ms|3ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.
  Describing should not contain the token AreaPathToken
    [-] No files Should contain unreplaced tokens 5ms (3ms|2ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.
  Describing should not contain the token AadAppIdToken
    [-] No files Should contain unreplaced tokens 5ms (3ms|2ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.
  Describing should not contain the token AadObjectIdToken
    [-] No files Should contain unreplaced tokens 5ms (3ms|2ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.
  Describing should not contain the token AadTenantIdToken
    [-] No files Should contain unreplaced tokens 6ms (3ms|3ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.
  Describing should not contain the token RolloutSpecEmailAliasToken
    [-] No files Should contain unreplaced tokens 12ms (9ms|3ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.
  Describing should not contain the token IcmPathToken
    [-] No files Should contain unreplaced tokens 7ms (4ms|3ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.
  Describing should not contain the token MdmAccountToken
    [-] No files Should contain unreplaced tokens 9ms (7ms|2ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.
  Describing should not contain the token MdmNamespaceToken
    [-] No files Should contain unreplaced tokens 6ms (3ms|3ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.
  Describing should not contain the token MicroserviceNameTokenLower
    [-] No files Should contain unreplaced tokens 5ms (3ms|2ms)
     ParameterBindingValidationException: Cannot bind argument to parameter 'Path' because it is null.

[fflaten]

$fullName is undefined. You need to store the variable using a BeforeAll block like you've done with $token.

Tip: I'd recommend moving $allFiles = ... and $tokens = .. inside a BeforeDiscovery-block. Just cosmetic, but shows intent and that it's not forgotten v4-code.

[DkSkydancer]

Beautiful, worked like a charm. Thank you!!!

For info, this is what i chagned my test to:

#Requires -Version 7.1

[CmdletBinding()]
param(
  [string]$TestRoot
)

BeforeDiscovery {
  Write-Host "Directory for discovery: $($TestRoot)"
  $allFiles = Get-ChildItem -Path $TestRoot -Include '*.*' -Recurse -File
  $tokens = @('TeamNameToken', 'MicroserviceNameToken', 'ServiceTreeIdToken', 'AreaPathToken', 'AadAppIdToken', 'AadObjectIdToken', 'AadTenantIdToken', 'RolloutSpecEmailAliasToken', 'IcmPathToken', 'MdmAccountToken', 'MdmNamespaceToken', 'MicroserviceNameTokenLower')
} 

Describe 'Verifying that all tokens have been replaced in all generated files' {
  Describe '"Finding leftover tokens in <fullName>"' -ForEach $allFiles {
    BeforeAll {
      # Renaming the automatic $_ variable to $fullNameto make it easier to work with
      $fullName = $_
    }
    Describe 'should not contain the token <token>' -ForEach $tokens {
      BeforeAll {
        # Renaming the automatic $_ variable to $token to make it easier to work with
        $token = $_
      }
      It 'No files Should contain unreplaced tokens' {
        $fullName | Should -Not -FileContentMatch $token
      }
    }
  }
}