Isolating Windows Registry Operations using the TestRegistry

TestRegistry is a Windows-only PowerShell PSDrive used to isolate registry based tests.

Pester creates a temporary, randomly named (a guid), registry key in the current user's hive under HKCU:\Software\Pester which is accessible as TestRegistry:.

Scoping

Basic scoping rules are implemented for the TestRegistry in a similar way to TestDrive:

1. A clean TestRegistry is created per container (test-file or scriptblock) on entry to the first top-level block (Describe or Context) in that container.
2. All keys and values created by your setups and tests are available during the lifetime of that block, including inner blocks and tests.
3. All keys are removed when exiting the block they were created in. Keys created in parent blocks is kept until that block is finished.
4. When the whole container is finished, the temporary registry key is deleted and all the subkeys and values with it.

Cleanup is done at key-level

Be aware that cleanup in TestRegistry currently works on registry key-level. Values created inside an existing key from the parent block will persist until the key itself is deleted when the parent block is finished.

Example

Function Get-InstallPath($path, $key) {
    Get-ItemProperty -Path $path -Name $key | Select-Object -ExpandProperty $key
}

Describe "Get-InstallPath" {

    New-Item -Path TestRegistry:\ -Name TestLocation
    New-ItemProperty -Path "TestRegistry:\TestLocation" -Name "InstallPath" -Value "C:\Program Files\MyApplication"

    It 'reads the install path from the registry' {
        Get-InstallPath -Path "TestRegistry:\TestLocation" -Key "InstallPath" | Should -Be "C:\Program Files\MyApplication"
    }
}