Update ShouldReturnZeroExitCode function

pester-extensions.psm1

@@ -6,28 +6,29 @@ Pester extension that allows to run command and validate exit code
 #>
 function ShouldReturnZeroExitCode {
     Param(
-        [Parameter (Mandatory = $true)] [ValidateNotNullOrEmpty()]
+        [String] $ActualValue,
-        [String]$ActualValue,
+        [switch] $Negate,
-        [switch]$Negate
+        [string] $Because # This parameter is unused by we need it to match Pester asserts signature
     )
 
-    Write-Host "Run command '${ActualValue}'"
+    $result = Get-CommandResult $ActualValue
-    Invoke-Expression -Command $ActualValue | ForEach-Object { Write-Host $_ }
-    $actualExitCode = $LASTEXITCODE
 
-    [bool]$succeeded = $actualExitCode -eq 0
+    [bool]$succeeded = $result.ExitCode -eq 0
     if ($Negate) { $succeeded = -not $succeeded }
 
     if (-not $succeeded)
     {
-        $failureMessage = "Command '${ActualValue}' has finished with exit code ${actualExitCode}"
+        $commandOutputIndent = " " * 4
+        $commandOutput = ($result.Output | ForEach-Object { "${commandOutputIndent}${_}" }) -join "`n"
+        $failureMessage = "Command '${ActualValue}' has finished with exit code ${actualExitCode}`n${commandOutput}"
     }
 
-    return New-Object PSObject -Property @{
+    return [PSCustomObject] @{
         Succeeded      = $succeeded
         FailureMessage = $failureMessage
     }
 }
 
-Add-AssertionOperator -Name ReturnZeroExitCode `
+if (Get-Command -Name Add-AssertionOperator -ErrorAction SilentlyContinue) {
-                    -Test  $function:ShouldReturnZeroExitCode
+    Add-AssertionOperator -Name ReturnZeroExitCode -InternalName ShouldReturnZeroExitCode -Test ${function:ShouldReturnZeroExitCode}
+}