Implement Get-Error cmdlet as Experimental Feature (#10727)

test/powershell/Modules/Microsoft.PowerShell.Utility/Get-Error.Tests.ps1

@@ -0,0 +1,93 @@
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License.
+
+Describe 'Get-Error tests' -Tag CI {
+    BeforeAll {
+        $skipTest = -not $EnabledExperimentalFeatures.Contains('Microsoft.PowerShell.Utility.PSGetError')
+        if ($skipTest) {
+            Write-Verbose "Test Suite Skipped. The test suite requires the experimental feature 'Microsoft.PowerShell.Utility.PSGetError' to be enabled." -Verbose
+            $originalDefaultParameterValues = $PSDefaultParameterValues.Clone()
+            $PSDefaultParameterValues["it:skip"] = $true
+        }
+    }
+
+    AfterAll {
+        if ($skipTest) {
+            $global:PSDefaultParameterValues = $originalDefaultParameterValues
+        }
+    }
+
+    It 'Get-Error resolves $Error[0] and includes InnerException' {
+        try {
+            1/0
+        }
+        catch {
+        }
+
+        $out = Get-Error | Out-String
+        $out | Should -BeLikeExactly '*InnerException*'
+    }
+
+    It 'Get-Error -Newest `<count>` works: <scenario>' -TestCases @(
+        @{ scenario = 'less than total'; count = 1; paramname = 'Newest' }
+        @{ scenario = 'equal to total'; count = 2; paramname = 'Last' }
+        @{ scenario = 'greater than total'; count = 9999; paramname = 'Newest' }
+    ){
+        param ($count, $paramname)
+
+        try {
+            1/0
+        }
+        catch {
+        }
+
+        try {
+            get-item (new-guid) -ErrorAction SilentlyContinue
+        }
+        catch {
+        }
+
+        $params = @{ $paramname = $count }
+
+        $out = Get-Error @params
+
+        $expected = $count
+        if ($count -eq 9999) {
+            $expected = $error.Count
+        }
+
+        $out.Count | Should -Be $expected
+    }
+
+    It 'Get-Error -Newest with invalid value `<value>` should fail' -TestCases @(
+        @{ value = 0 }
+        @{ value = -2 }
+    ){
+        param($value)
+
+        { Get-Error -Newest $value } | Should -Throw -ErrorId 'ParameterArgumentValidationError,Microsoft.PowerShell.Commands.GetErrorCommand'
+    }
+
+    It 'Get-Error will accept pipeline input' {
+        try {
+            1/0
+        }
+        catch {
+        }
+
+        $out = $error[0] | Get-Error | Out-String
+        $out | Should -BeLikeExactly '*-2146233087*'
+    }
+
+    It 'Get-Error will handle Exceptions' {
+        try {
+            Invoke-Expression '1/d'
+        }
+        catch {
+        }
+
+        $out = Get-Error | Out-String
+        $out | Should -BeLikeExactly '*ExpectedValueExpression*'
+        $out | Should -BeLikeExactly '*UnexpectedToken*'
+    }
+}