Pesterでカスタムアサーションを行うサンプル(Pester 4.0.5以降)

Invoke-PesterCustomAssertionSampleEx.ps1

# Pester 4.0.5以降で動作
Import-Module Pester -MinimumVersion 4.0.5 -Force

function PesterBeHash($Value, $Expected) {
    if (-not ($Value -is [Hashtable] -and $Expected -is [Hashtable])) {
        return $Value -eq $Expected
    }
    if ($Value.Keys.Count -ne $Expected.Keys.Count) {
        return $false
    }
    foreach ($key in $Value.Keys) {
        if ($Value[$key] -ne $Expected[$key]) {
            return $false
        }
    }
    return $true
}

Function PesterBeHashFailureMessage($Value, $Expected) {
    $e = ""
    if ($Expected -is [Hashtable]) {
        foreach ($key in $Expected.Keys) {
            if ($e -ne "") { $e += ";" }
            $e += "{0}={1}" -f $key, $Expected[$key]
        }
    } else {
        $e = "[{0}] {1}" -f ($Expected.GetType()), [string]$Expected
    }
    $v = ""
    if ($Value -is [Hashtable]) {
        foreach ($key in $Value.Keys) {
            if ($v -ne "") { $v += ";" }
            $v += "{0}={1}" -f $key, $Value[$key]
        }
    } else {
        $v = "[{0}] {1}" -f ($Value.GetType()), [string]$Value
    }
    return "Expected: {0}`nBut was: {1}" -f $e, $v
}

Function NotPesterBeHashFailureMessage($Value, $Expected) {
    return PesterBeHashFailureMessage -Value $Value -Expected $Expected
}

# 新しく登録する関数
function BeHash($ActualValue, $ExpectedValue, [switch]$Negate) {
    [bool]$succeeded = PesterBeHash -Value $ActualValue -Expected $ExpectedValue
    if ($Negate) {
        $succeeded = -not $succeeded
    }
    
    if (-not $succeeded) {
        if ($Negate) {
            $failureMessage = NotPesterBeHashFailureMessage -Value $ActualValue -Expected $ExpectedValue
        } else {
            $failureMessage = PesterBeHashFailureMessage -Value $ActualValue -Expected $ExpectedValue
        }
    }

    return New-Object PSOBject -Property @{
        Succeeded      = $succeeded
        FailureMessage = $failureMessage
    }
}

Add-AssertionOperator -Name BeHash -Test $function:BeHash -Alias 'Hash'

Describe "カスタムアサーションのサンプル" {
    # Should Be ではハッシュは比較できない
    It "通常のアサーションで失敗する例" {
        @{ Name = "田中"; Salary = 300 } | Should -Be @{ Name = "田中"; Salary = 300 }
    }

    # カスタムアサーションでハッシュを比較してみる
    It "カスタムアサーション成功例" {
        @{ Name = "田中"; Salary = 300 } | Should -BeHash @{ Name = "田中"; Salary = 300 }
    }
    It "カスタムアサーション失敗例" {
        @{ Name = "鈴木"; Salary = 300 } | Should -BeHash @{ Name = "田中"; Salary = 300 }
    }
}