Providing test cases to Pester V5 test - powershell

Question

I'm trying to write a pester test (v5) to see if various services are running on remote computers. This is what I have, which works:
$Hashtable = #(
#{ ComputerName = "computer1"; ServiceName = "serviceA" }
#{ ComputerName = "computer1"; ServiceName = "serviceB" }
#{ ComputerName = "computer2" ; ServiceName = "serviceB" }
)
Describe "Checking services" {
It "check <ServiceName> is running on <ComputerName>" -TestCases $Hashtable {
( get-service -computername $ComputerName -name $ServiceName ).status | Should -be "Running"
}
}
My question is around providing the test data to the test (i.e. the list of computer names and services). Suppose I want to add more services to this list. At the moment, I would be modifying my pester file by adding more services to $Hashtable. It doesn't feel quite right to be doing this to me, and I'd like to get the approach correct at this early stage. My gut tells me that the list of services should be separated from the pester file. Then running the test would involve importing the list of services somehow. Does anyone know if I am going about this the wrong way?
Thanks for any help
Andrew

Answer 1

If the list of servers and services will change often, it would be a good idea to read it from a separate file, especially if you have the tests under version control. This way you can easily see in the history that only the test data has changed, but the test logic didn't.
A good file format for the given test data would be CSV:
ComputerName, ServiceName
computer1, serviceA
computer1, serviceB
computer2, serviceB
You can read the CSV using Import-Csv, but you have to convert each row to a hashtable, because Pester expects an array of hashtables for the -TestCases parameter. Import-Csv outputs an array of PSCustomObject though.
BeforeDiscovery {
$script:testCases = Import-Csv $PSScriptRoot\TestCases.csv | ForEach-Object {
# Convert row (PSCustomObject) to hashtable.
$hashTable = #{}
$_.PSObject.Properties | ForEach-Object { $hashTable[ $_.Name ] = $_.Value }
# Implicit output that will be captured in array $script:testCases
$hashTable
}
}
Describe "Checking services" {
It "check <ServiceName> is running on <ComputerName>" -TestCases $script:testCases {
( get-service -computername $ComputerName -name $ServiceName ).status | Should -be "Running"
}
}
Note: While not strictly necessary I have put the code that reads the test cases into the BeforeDiscovery section, as suggested by the docs. This makes our intentions clear.