Dynamically creating mocks from data?

[OneFineDev]

I'm mocking filtered calls to Get-MgUser with a bunch of user objects I have exported to CliXml, that look like this in the function code:

$User = Get-MgUser -UserId $RoleAssignment.PrincipalId

And like this in the test file

                $MockLookup = @{}

                foreach ($User in $UserData) {
                    $MockLookup[$User.Id] = $User
                }

                Mock Get-MgUser { $Mocklookup['787af109-31dc-4adf-9c7d-fd310c04360a'] } -ParameterFilter { $UserId -eq '787af109-31dc-4adf-9c7d-fd310c04360a' }
                Mock Get-MgUser { $Mocklookup['1530541d-810b-4c8b-b33c-27136e72255b'] } -ParameterFilter { $UserId -eq '1530541d-810b-4c8b-b33c-27136e72255b' }
                Mock Get-MgUser { $Mocklookup['f4ae2b54-2052-4fdd-a9a5-c2955d4cf65c'] } -ParameterFilter { $UserId -eq 'f4ae2b54-2052-4fdd-a9a5-c2955d4cf65c' }
                Mock Get-MgUser { $Mocklookup['01fcdc0e-d4db-404e-83c8-3d4f36bb7c28'] } -ParameterFilter { $UserId -eq '01fcdc0e-d4db-404e-83c8-3d4f36bb7c28' }
                Mock Get-MgUser { $Mocklookup['3c962d06-8d15-4e32-a575-ee99cb9b1b44'] } -ParameterFilter { $UserId -eq '3c962d06-8d15-4e32-a575-ee99cb9b1b44' }
                Mock Get-MgUser { $Mocklookup['e815063e-9339-4d96-b28b-c475afa6a7c5'] } -ParameterFilter { $UserId -eq 'e815063e-9339-4d96-b28b-c475afa6a7c5' }
                Mock Get-MgUser { $Mocklookup['551940b1-70b6-4f20-847b-1853466664ad'] } -ParameterFilter { $UserId -eq '551940b1-70b6-4f20-847b-1853466664ad' }
                Mock Get-MgUser { $Mocklookup['ce5f1cd6-70bd-4482-a38f-37c47cdad0d6'] } -ParameterFilter { $UserId -eq 'ce5f1cd6-70bd-4482-a38f-37c47cdad0d6' }
                Mock Get-MgUser { $Mocklookup['bec6779f-ab5d-42de-920f-62c65ea6eb39'] } -ParameterFilter { $UserId -eq 'bec6779f-ab5d-42de-920f-62c65ea6eb39' }
                Mock Get-MgUser { $Mocklookup['bd3cc1b4-3c46-4b1f-ad54-a3daeb49b1d6'] } -ParameterFilter { $UserId -eq 'bd3cc1b4-3c46-4b1f-ad54-a3daeb49b1d6' }
                Mock Get-MgUser { $Mocklookup['a4781600-3d02-4de7-a2b2-5644b8ed69b2'] } -ParameterFilter { $UserId -eq 'a4781600-3d02-4de7-a2b2-5644b8ed69b2' }
                Mock Get-MgUser { $Mocklookup['46e1d71f-0b21-46eb-a562-90709e1695a2'] } -ParameterFilter { $UserId -eq '46e1d71f-0b21-46eb-a562-90709e1695a2' }
                Mock Get-MgUser { $Mocklookup['5d07cf6c-b3fd-4208-85ab-3a7c3f8c7747'] } -ParameterFilter { $UserId -eq '5d07cf6c-b3fd-4208-85ab-3a7c3f8c7747' }

This works, but is obviously horrible. I imagine there is a way to generate mocks dynamically, with a naive implementation (that doesn't work ) like:

      $mockLookup.GetEnumerator() | ForEach-Object {
          Mock Get-MgUser { $MockLookup[$($_.Key)] } -ParameterFilter { $UserId -eq $($_.Value.Id) } 
      }

but I suspect scoping nuances beyond my understanding are at play. It feels like a riff on this but I've not managed to transpose it...

Any help, much appreciated.

[nohwnd]

Is this a simplified example? Looks to me that you could simply add a single mock with no filter and return the data from the $MockLookup table based on $UserId

Mock Get-MgUser { $Mocklookup[$UserId] }

[OneFineDev]

Apologies for the brevity, but I think you got it anyway - that seems to work!

Ok, so am I right in thinking that the values passed to parameters on the "real" command (i.e. -UserId for Get-MgUser in this case) are then available to that call of the mocked command in the test file?

I'm assuming that's how the mock can lookup the key in the lookup table in the testfile?

Mock Get-MgUser { $Mocklookup[$UserId] }

Actually, "available" is the wrong word I guess; is the parameter value being resolved in the test scope when the mock gets registered?

Mock: We are in a test. Finding all behaviors in this test. 
Mock: Found behaviors for 'Get-MgUser' in the test. 
Mock: Finding all behaviors in this block and parent blocks. 
Mock: Found 0 behaviors in all parent blocks, and 1 behaviors in test. 
Mock: Filtering behaviors for command Get-MgUser, for target module NCR.PermissionsManagement (Showing all behaviors for this command, actual filtered list is further in the log, look for 'Filtered parametrized behaviors:' and 'Filtered default behaviors:'):      
Mock: Behavior is a default behavior from the target module NCR.PermissionsManagement, saving it:
     Target module: NCR.PermissionsManagement
     Body: { $Mocklookup[$UserId] }
     Filter: $null
     Default: $true
     Verifiable: $false
Mock: We are in a test. Returning mock table from test scope. 
Mock: Filtered parametrized behaviors:
$null
Mock: Filtered default behavior:
     Target module: NCR.PermissionsManagement
     Body: { $Mocklookup[$UserId] }
     Filter: $null
     Default: $true
     Verifiable: $false
Mock: Finding behavior to use, one that passes filter or a default: 
Mock: {  $Mocklookup[$UserId]  } is a default behavior and will be used for the mock call.
Mock: Executing mock behavior for mock NCR.PermissionsManagement - Get-MgUser. 
Mock: Behavior for NCR.PermissionsManagement - Get-MgUser was executed. 

Or am I talking rubbish? 🤣 Must go and read all the docs again.
Anyway, thanks for taking the time to help.

[fflaten]

All parameters in the original command are available in the mock as well.

Whatever parameters you invoke the mock with, e.g. -UserId 123, is available through $UserId and $PesterBoundParameters.UserId in the mock scriptblock.

Btw. If you need to fallback to the real Get-MgUser for users not in $mocklookup, you can use follow this example to call the real cmdlet using Get-Command -CommandType Cmdlet inside the mock.