Pester test if list is empty do not run the tests

Question

I would like to be able to skip tests if list is empty.

a very simplified example:

No name is -eq to "jens", therefore the $newlist would be empty, and of course the test will fail, but how do i prevent it from going though this test if the list is empty?

context {
    BeforeAll{
    $List = @(Harry, Hanne, Hans)
    $newlist = @()
    
    foreach ($name in $List) {
        if (($name -eq "Jens")) {
            $name += $newlist
    }
    }
    }
    It "The maximum name length is 10 characters" {
        $newlist |ForEach-Object {$_.length | Should -BeIn (1..10) -Because "The maximum name length is 10 characters"}
    }
}

fail message:

Expected collection @(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) to contain 0, because The maximum name length is 10 characters, but it was not found.

Answer 1

You can achieve this by using Set-ItResult, which is a Pester cmdlet that allows you to force a specific result. For example:

Describe 'tests' {
    context 'list with content' {

        BeforeAll {
            $List = @('Harry', 'Hanne', 'Hans')
            $newlist = @()
    
            foreach ($name in $List) {
                if (($name -eq "Jens")) {
                    $newlist += $name
                }
            }
        }
        
        It "The maximum name length is 10 characters" {
            if (-not $newlist) {
                Set-ItResult -Skipped
            }
            else {
                $newlist | ForEach-Object { $_.length | Should -BeIn (1..10) -Because "The maximum name length is 10 characters" }
            }
        }
    }
}

Note that there was an error in your example ($newlist wasn't being updated with name, you were doing the reverse) which I've corrected above, but your test doesn't actually fail for me in this example (before adding the Set-ItResult logic). I think this is because by using ForEach-Object with an empty array as an input the Should never gets executed when its empty, so with this approach your test would just pass because it never evaluates anything.