Should -HaveParameter -DefaultValue does not work for boolean types or integer value of 0 (regression)

[phoerr]

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• I have searched the existing issues. See all issues
• I have tested using the latest version of Pester. See Installation and update guide.

What is the issue?

Pester version 5.4.1 has a regression from 5.4.0 where Should -HaveParameter -DefaultValue no longer works for the following kinds of tests that previously passed:

• Function parameter of type [int] with a default value of 0
• Function parameter of type [bool] with any default value set (both $true and $false)

Sample test

Describe 'Parameter default value tests' {
    BeforeAll {
        function Test-Parameter {
            param (
                [Parameter()]
                [int]$intParam = 0,

                [Parameter()]
                [bool]$boolTrueParam = $true,

                [Parameter()]
                [bool]$boolFalseParam = $false
            )
        }
    }

    It 'Default value when integer is zero' {
        Get-Command Test-Parameter | Should -HaveParameter 'intParam' -Type 'int' -DefaultValue 0
    }

    It 'Default value for true boolean' {
        Get-Command Test-Parameter | Should -HaveParameter 'boolTrueParam' -Type 'bool' -DefaultValue $true
    }

    It 'Default value for false boolean' {
        Get-Command Test-Parameter | Should -HaveParameter 'boolFalseParam' -Type 'bool' -DefaultValue $false
    }
}

In Pester 5.4.0, these worked as expected:

Running tests from 'C:\source\PesterBug\Test-Parameter.Tests.ps1'
Describing Parameter default value tests
  [+] Default value when integer is zero 36ms (6ms|30ms)
  [+] Default value for true boolean 6ms (5ms|2ms)
  [+] Default value for false boolean 14ms (6ms|9ms)
Tests completed in 217ms
Tests Passed: 3, Failed: 0, Skipped: 0 NotRun: 0

In Pester 5.4.1, these fail with:

[-] Parameter default value tests.Default value for integer 8ms (7ms|1ms)
 Expected command Test-Parameter to have a parameter intParam, of type [System.Int32] and the default value to be '0', but the default value was <empty>.
 at Get-Command Test-Parameter | Should -HaveParameter 'intParam' -Type 'int' -DefaultValue 0, C:\source\PesterBug\Test-Parameter.Tests.ps1:21
 at <ScriptBlock>, C:\source\PesterBug\Test-Parameter.Tests.ps1:21
[-] Parameter default value tests.Default value for true boolean 17ms (16ms|1ms)
 Expected command Test-Parameter to have a parameter boolTrueParam, of type [System.Boolean] and the default value to be 'True', but the default value was '$true'.
 at Get-Command Test-Parameter | Should -HaveParameter 'boolTrueParam' -Type 'bool' -DefaultValue $true, C:\source\PesterBug\Test-Parameter.Tests.ps1:25
 at <ScriptBlock>, C:\source\PesterBug\Test-Parameter.Tests.ps1:25
[-] Parameter default value tests.Default value for false boolean 19ms (18ms|1ms)
 Expected command Test-Parameter to have a parameter boolFalseParam, of type [System.Boolean] and the default value to be 'False', but the default value was '$false'.
 at Get-Command Test-Parameter | Should -HaveParameter 'boolFalseParam' -Type 'bool' -DefaultValue $false, C:\source\PesterBug\Test-Parameter.Tests.ps1:29
 at <ScriptBlock>, C:\source\PesterBug\Test-Parameter.Tests.ps1:29

Regression

This appears to have been caused by ea70451. I used a debugger to check the value of $paramInfo in Get-ParameterInfo and it looks different when the function was changed to use the AST.

Boolean before and after

# Pester 5.4.0
Name      Type      DefaultValue DefaultValueType
----      ----      ------------ ----------------
boolParam [bool]    true         Variable

# Pester 5.4.1
Name      Type      DefaultValue DefaultValueType
----      ----      ------------ ----------------
boolParam [boolean] $true        Boolean

Integer before and after

# Pester 5.4.0
Name     Type    DefaultValue DefaultValueType
----     ----    ------------ ----------------
intParam [int]   0            Number

# Pester 5.4.1
Name     Type    DefaultValue DefaultValueType
----     ----    ------------ ----------------
intParam [int32] 0            Int32

Expected Behavior

These kind of tests with -DefaultValue should pass.

Steps To Reproduce

See working sample test above in issue description

Describe your environment

Pester version     : 5.4.1 C:\Users\phoerr\Documents\PowerShell\Modules\Pester\5.4.1\Pester.psm1
PowerShell version : 7.3.6
OS version         : Microsoft Windows NT 10.0.19045.0

Possible Solution?

No response

[fflaten]

Thanks for the detailed report and troubleshooting!

You're right about the cause. Looks like it broke in 5.4.1 due to #2288 which introduced the ast-logic. Will look into it later.

[nohwnd]

The problem is at least this cast: https://github.com/pester/Pester/pull/2288/files#diff-48c3c91280455432daa49020cc6c75e8670271729e764a963b227d9c9168a1feR213

This would return false for any falsy default value. We need an additional bool flag, or a value descriptor as the original api has.

Investigating and writing some tests.