Pester 5 MockUp Fails on SwitchParamater

gistfile1.txt

BeforeAll {
    Remove-Module -Name 'DscResource.Common' -Force
    New-Module -Name 'DscResource.Common' -ScriptBlock {
        function Assert-Module
        {
            [CmdletBinding()]
            param
            (
                [Parameter(Mandatory = $true)]
                [System.String]
                $ModuleName,

                [Parameter()]
                [System.Management.Automation.SwitchParameter]
                $ImportModule
            )

            if (-not (Get-Module -Name $ModuleName -ListAvailable))
            {
                $errorMessage = $script:localizedData.ModuleNotFound -f $ModuleName
                New-ObjectNotFoundException -Message $errorMessage
            }

            if ($ImportModule)
            {
                Import-Module -Name $ModuleName
            }
        }
    } | Import-Module

    $script:moduleName = 'DscResource.Common'
}

Describe 'Assert-Module' {
    BeforeAll {
        $testModuleName = 'TestModule'
    }

    Context 'When module is available' {
        BeforeAll {
            Mock -CommandName Import-Module -ModuleName 'DscResource.Common'
            Mock -CommandName Get-Module -MockWith {
                return @{
                    Name = $testModuleName
                }
            } -ModuleName 'DscResource.Common'
        }

        Context 'When module should be imported' {
            It 'Should not throw an error' {
                { Assert-Module -ModuleName $testModuleName -ImportModule } | Should -Not -Throw
            }

            It 'Should call the expected mocks' {
                Should -Invoke -CommandName Import-Module -Exactly -Times 1 -Scope Context
            }
        }
    }
}