add test for reg key

Author: Steve Lee (POWERSHELL HE/HIM) (from Dev Box)

registry/tests/registry.config.set.tests.ps1

@@ -125,4 +125,24 @@ Describe 'registry config set tests' {
 
         Get-ItemProperty -Path 'HKCU:\1\2' -Name 'Test' -ErrorAction Ignore | Should -BeNullOrEmpty
     }
+
+    It 'Should succeed when _exist is false and key does not exist' -Skip:(!$IsWindows) {
+        $config = @{
+            '$schema' = 'https://aka.ms/dsc/schemas/v3/bundled/config/document.json'
+            resources = @(
+                @{
+                    name = 'reg'
+                    type = 'Microsoft.Windows/Registry'
+                    properties = @{
+                        keyPath = 'HKCU\1'
+                        _exist = $false
+                    }
+                }
+            )
+        }
+
+        $out = dsc config set -i ($config | ConvertTo-Json -Depth 10) | ConvertFrom-Json
+        $LASTEXITCODE | Should -Be 0
+        $out.results[0].result.afterState._exist | Should -Be $false
+    }
 }