自身功能的输出测试

我有一个返回配置文件内容的函数:

function Get-VA.Settings {
<#
.SYNOPSIS
Fetches settings from a XML file
.DESCRIPTION
Fetches settings from a XML file and outputs a XML Object
.EXAMPLE
Get-VA.Settings -path <path-to-config-file> -Rollback <path-to-rollback-file>
#>
  Param (
    [Parameter(Mandatory=$true,Position=0)]
    [string]$path,
    [Parameter(Mandatory=$true,Position=1)]
    [string]$Rollback
  )
  try {
    [xml]$config = Get-Content -Path $path
    Write-Output -InputObject $config
  } catch {
    Write-VA.EventLog -Message ("Could not load Configuration File: `r`n" + $Error) -Id 11 -type Error
    Invoke-VA.Rollback -Path $($Rollback)
  }
}

现在我在Pester中做了一个测试,它只是检查函数是否真的返回了什么:

Import-Module ($PSScriptRoot + "\utility.psm1")
Describe "Settings Module" {
  InModuleScope utility {
    Context "Get-VA.Settings" {
      It "should have Help and Examples" {
        $helpinfo = Get-Help Get-VA.Settings
        $helpinfo.examples | should not BeNullOrEmpty # should have examples
        $helpinfo.details | should not BeNullOrEmpty # should have Details
        $helpinfo.description | Should not BeNullOrEmpty # Should have a Description for the Function
      }

      It "should fail safely on read Error" {
        Mock Get-Content {throw}
        Mock Write-VA.EventLog { }
        Mock Invoke-VA.Rollback { }
        Get-VA.Settings -path "1" -Rollback "1"
        Assert-MockCalled Invoke-VA.Rollback -Times 1
      }

      It "should return a value" {
        Set-Content -Value "<xml><foo>bar</foo></xml>" -Path "settings-test.ps1" 
        Get-VA.Settings -path .\settings-test.ps1 -Rollback "1" | should not BeNullOrEmpty
        Remove-Item "settings-test.ps1"
      }
    }
  }
}

现在,无论我如何输出配置设置,我似乎都无法通过Pester的测试,即使功能正常运行也很困难。

[-]应返回值18ms
应为:值不能为空
获取ConfigSettings-路径.\settings测试。ps1-回滚“1”|不应为NullOrEmpty

我错过了什么吗?那么如何正确处理函数输出?