How to get Pester to see custom Should operators?

[kamranayub]

I must be missing something simple because I feel really close.

I have defined a new PesterBeDate function and failure functions. According to what I see in the Should assertion source, it should be able to find my command. In fact if I run:

Get-Command PesterBeDate -CommandType Function

I see the command output. But for some reason Pester doesn't:

RuntimeException: 'BeDate' is not a valid Should operator.
   at Get-TestResult, C:\Program Files\WindowsPowerShell\Modules\Pester\3.4.2\Functions\Assertions\Should.ps1: line 42

[dlwyatt]

Just put your function into a PS1 file in the Pester\Functions\Assertions directory, and reload the module. Should be all set. :)

[kamranayub]

Ah, but this for an OSS project... Is there a way to source Pester not from
global? Or any other way to "extend" Pester so people don't need to do custom stuff to contribute?

On Fri, Aug 12, 2016, 12:31 Dave Wyatt [email protected] wrote:

Just put your function into a PS1 file in the Pester\Functions\Assertions
directory, and reload the module. Should be all set. :)

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[dlwyatt]

It probably depends on where you've defined those functions. Unless they're in the global scope, Pester's calls to Get-Command aren't going to find them. (The way that Should operators get loaded is also changing in v4.)

However, for now, you can inject your functions into Pester's scope after loading the module and it should work:

$pesterModule = Import-Module Pester -PassThru

. $pesterModule {
    function PesterBeDate { }
    # etc
}

Edit: I'm not 100% certain whether you need to use the . operator here, but I changed the code to be on the safe side. Otherwise the functions might be discarded when your script block goes out of scope.

[kamranayub]

Thanks, I did end up sourcing a local module for better out of the box
tests for contributors. Then just copying any assertions after the fact and
that works fine.

On Mon, Aug 15, 2016, 20:24 Dave Wyatt [email protected] wrote:

It probably depends on where you've defined those functions. Unless
they're in the global scope, Pester's calls to Get-Command aren't going to
find them. (The way that Should operators get loaded is also changing in
v4.)

However, for now, you can inject your functions into Pester's scope after
loading the module and it should work:

$pesterModule = Import-Module Pester -PassThru
& $pesterModule {
function PesterBeDate { }
# etc
}

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[kamranayub]

Here's an example of what I did for future reference: https://github.com/kamranayub/posh-openweathermap/blob/afe931f979dd675c279eecd89028f3fe7c4a5893/Run-Tests.ps1

[ryangribble]

(The way that Should operators get loaded is also changing in v4.)

Hey guys, is there any information about how these have changed in v4? Ive been unsuccesful in located instructions on how to do custom Should extensions in the new version?

[dlwyatt]

Didn't write instructions yet, will get to that this weekend. However, you can look at https://github.com/pester/Pester/blob/master/Functions/Assertions/Be.ps1 for guidance. Three main changes:

• You have to call Add-AssertionOperator to register your operator with Pester.
• Your test function now has to return an object with Succeeded (boolean) and FailureMessage (string) properties. FailureMessage is ignored unless Succeeded is $false.
• Your test function, at a minimum, must take three parameters: $ActualValue, $ExpectedValue, [switch] $Negate. -Negate is the equivalent of what we used to do with separate functions (PesterBeFailureMessage and NotPesterBeFailureMessage, etc.) If you add any other named parameters to your test function, they'll show up as dynamic parameters when Should is called with your operator.

The names of your functions don't matter anymore. You can add aliases for your operator with the -Alias parameter on Add-AssertionOperator. If your operator can handle entire arrays, you can add the -SupportsArrayInput switch, and anything that gets piped to Should will be passed in as an array to a single call of your operator in the $ActualValue parameter. If you don't use -SupportsArrayInput, then piped in elements to Should will get tested one at a time, same as how everything worked in v3.

[dlwyatt]

Actually, Be.ps1 is probably one of the more complex files. Here's a simple one: https://github.com/pester/Pester/blob/master/Functions/Assertions/BeGreaterThan.ps1

[ryangribble]

Thanks for the info @dlwyatt

It doesn't seem like Add-AssetionOperator is an exported command though? Running version 4.0.3

PS C:\Users\ryan.gribble> Get-Command -Module Pester -Name Add-*

<nothing>



PS C:\Users\ryan.gribble> Get-Command -Module Pester

CommandType     Name                                               Version    Source
-----------     ----                                               -------    ------
Function        AfterAll                                           4.0.3      pester
Function        AfterEach                                          4.0.3      pester
Function        AfterEachFeature                                   4.0.3      pester
Function        AfterEachScenario                                  4.0.3      pester
Function        Assert-MockCalled                                  4.0.3      pester
Function        Assert-VerifiableMocks                             4.0.3      pester
Function        BeforeAll                                          4.0.3      pester
Function        BeforeEach                                         4.0.3      pester
Function        BeforeEachFeature                                  4.0.3      pester
Function        BeforeEachScenario                                 4.0.3      pester
Function        Context                                            4.0.3      pester
Function        Describe                                           4.0.3      pester
Function        Find-GherkinStep                                   4.0.3      pester
Function        Get-MockDynamicParameters                          4.0.3      pester
Function        Get-TestDriveItem                                  4.0.3      pester
Function        GherkinStep                                        4.0.3      pester
Function        In                                                 4.0.3      pester
Function        InModuleScope                                      4.0.3      pester
Function        Invoke-Gherkin                                     4.0.3      pester
Function        Invoke-GherkinStep                                 4.0.3      pester
Function        Invoke-Mock                                        4.0.3      pester
Function        Invoke-Pester                                      4.0.3      pester
Function        It                                                 4.0.3      pester
Function        Mock                                               4.0.3      pester
Function        New-Fixture                                        4.0.3      pester
Function        New-MockObject                                     4.0.3      pester
Function        New-PesterOption                                   4.0.3      pester
Function        SafeGetCommand                                     4.0.3      pester
Function        Set-DynamicParameterVariables                      4.0.3      pester
Function        Set-TestInconclusive                               4.0.3      pester
Function        Setup                                              4.0.3      pester
Function        Should                                             4.0.3      pester

[dlwyatt]

That's correct, though there's a PR open right now to change that.

[stuartleeks]

I've just installed 4.0.4 to try to update a couple of libraries with custom assertions and am hitting this issue. I can't see Add-AssertionOperator

[nohwnd]

#765 merged need to release new version

[stuartleeks]

Thanks @nohwnd. Do you have any idea of timelines for a new release now that this is merged?

[it-praktyk]

@stuartleeks , please read #793.

[stuartleeks]

Thanks @it-praktyk, I read through #793 when I was trying to track down my issue. I guess the questions I was really asking is whether there will be a release ahead of a final v4 release (as there still seems to be a list of issues before then) :-)

[nohwnd]

@stuartleeks it's released as 4.0.5. Closing this issue, feel free to reopen if you need more help.

[stuartleeks]

Awesome, thanks @nohwnd !