Help - turning my script into Pester

Question

Help - turning my script into Pester

ZM 211

hi im sturggling with pester and i wanted to ask if you could help me out.

i want to turn this script below in pester, would you be able to do that?

[Cmdletbinding()]
param
(
[Parameter(Mandatory)]
[ValidateNotNullOrEmpty()]
[string]
$Regex
)

$Result = [Guid]::empty
[Guid]::TryParse("$Regex", [System.Management.Automation.PSReference]$Result)

if (-not [Guid]::TryParse("$Regex", [System.Management.Automation.PSReference]$Result))
{
Write-error "The Guid entered is incorrect"
}

1 answer

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Answer 1

Rich Matheisen 47,901

If you're struggling with understanding Pester you should consider ordering this book: pesterbook, or you can find many examples of using Pester on the web. The problem with using the web is that the things you find there may not be what you want to accomplish, or they cover a narrow topic and you have to go look for more information. The book, at least, puts in all (or most of it) in one place.

But I don't understand what you want to do here. Pester would probably be used to write tests that cover the data you expect to be submitted to your function and the results returned from the function. In other words, Pester would load your module/function and then calling that function with data and examining the result, comparing it against your stated expectations. If the function is called using a valid GUID you'd expect a value of $TRUE to be returned. If it was called using an invalid GUID your function should return $FALSE.

However, your function, when called with an invalid GUID returns $FALSE in the "success" stream AND a non-terminating exception in the "error" stream. To test that you'd need to be sure to set the default error action in those cases to "STOP" so you an intercept the exception (or change the design of the function to not generate the non-terminating error -- OR change the Write-Error cmdlet to a "Throw" statement to cause a terminating exception).

In your post you said that you "want to turn this script below in pester". What does that mean? Did you mean "test" instead or "turn"?

ZM 211 Reputation points

2022-04-26T08:04:22.56+00:00

@Rich Matheisen thank you for the response

Yes I would like to turn this code below into a Pester test using describe blocks and it blocks but I don't know how to. Could you help me with that?

[Cmdletbinding()]
param
(
[Parameter(Mandatory)]
[ValidateNotNullOrEmpty()]
[string]
$Regex
)

$Result = [Guid]::empty
[Guid]::TryParse("$Regex", [System.Management.Automation.PSReference]$Result)

if (-not [Guid]::TryParse("$Regex", [System.Management.Automation.PSReference]$Result))
{
Write-error "The Guid entered is incorrect"
}
Rich Matheisen 47,901 Reputation points

2022-04-26T19:31:45.1+00:00

I still don't understand what you want to do.

"Describe" is just a keyword ("Describe") followed by a description of what follows (i.e., what you're testing) followed by a script block.

In that script block you'd have a "Context" keyword followed by a description of the what the context script block is doing, followed by a script block.

In the Context script block you create the test cases -- each of which is a script block, all of which are stored an array.

Following the Context block you'd have an "it" keyword followed by a title for the test and a parameter "-TestCases" that takes the array defined in the Context block. The "it" block takes the parameters delivered by each test and the code that invokes the code you're testing and verifies what the tested code returns. It does that testing by using "Should Be", "Should BeExactly", "Should HaveCount", etc..

So . . . what are you going to test? What parameters will you supply to test with, what are the results to be tested, and what values should be expected from the function under test when supplied with your test data?

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Help - turning my script into Pester

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