Testing for mandatory parameters with Pester
Per the comments from Mathias, you can't really test for whether a Mandatory parameter is missing because PowerShell prompts for it rather than throwing an error. Per the comment he linked to from the Pester team you could use Get-Command
to test for the Mandatory parameter setting in the script (assuming it is the only parameter attribute set for that variable)
((Get-Command "$here\$sut").Parameters['ComputerName'].Attributes.Mandatory | Should Be $true
An alternative option would be to not use Mandatory parameters in this instance, and instead have a script block that does a Throw
as the default value of the parameter:
Param (
[String]$ComputerName = $(Throw '-ComputerName is required'),
[String]$ScriptName
)
If the script is always used as part of an automated process (instead of via user execution) this might be preferred as it allows you to control/capture its behavior and avoids it getting stuck during execution. You can then test the script as you had originally proposed:
Describe 'Mandatory paramters' {
it 'ComputerName' {
{
$Params = @{
#ComputerName = 'MyPc'
ScriptName = 'Test'
}
. "$here\$sut" @Params
} | Should throw '-ComputerName is required'
}
}