Adding Pester tests to existing code

Get-FromSFtp.ps1

Add-Type -Path (Join-Path -Path $psScriptRoot "Renci.SshNet.dll")

function Get-FromSFtp {
    $fileList=$null
    try {
        $sftp=New-Object Renci.SshNet.SftpClient("127.0.0.1","test","test")
        $sftp.Connect()
        if($sftp.IsConnected) {
            $sftp.ChangeDirectory("/test")
            $fileList=$sftp.ListDirectory(".")
        }
        return $fileList
    } catch [Exception] {
        Write-Host $_.Exception.ToString()
    } finally {
        if(($sftp -ne $null) -and ($sftp.IsConnected)) {
            $sftp.Disconnect()
        }
    }
}

Get-FromSFtp.Tests.ps1

$here = Split-Path -Parent $MyInvocation.MyCommand.Path
$sut = (Split-Path -Leaf $MyInvocation.MyCommand.Path).Replace(".Tests.", ".")
. "$here\$sut"

$mockSFtpCode = @"
public class MockSFtp {
    public bool ConnectCalled { get; private set; }
    public bool DisconnectCalled { get; private set; }
    public bool IsConnected { get; set; }
    public string ChangeDirectoryParam { get; private set; }
    public string ListDirectoryParam { get; private set; }

    public void Connect() {
        this.ConnectCalled = true;
    }

    public void Disconnect() {
        this.DisconnectCalled = true;
    }

    public void ChangeDirectory(string directory) {
        this.ChangeDirectoryParam = directory;
    }

    public string[] ListDirectory(string path) {
        this.ListDirectoryParam = path;
        return new string[] { "test1" };
    }
}
"@

$throwingMockSFtpCode = @"
public class ThrowingMockSFtp {
    public void Connect() {
        throw new System.Exception();
    }
}
"@

Add-Type -TypeDefinition $mockSFtpCode
Add-Type -TypeDefinition $throwingMockSFtpCode

Describe "Get-FromSFtp" {
    Context "when connected" {
        $mockSFtp = New-Object MockSFtp
        $mockSFtp.IsConnected = $true
        Mock New-Object -MockWith { $mockSFtp }
        $files = Get-FromSFtp

        It "attempts to connect to an sftp server" {
            $mockSFtp.ConnectCalled | Should Be $true
        }

        It "changes to the directory /test" {
            $mockSFtp.ChangeDirectoryParam | Should Be '/test'
        }

        It "gets the content listing of the directory" {
            $mockSFtp.ListDirectoryParam | Should Be '.'
            $files | Should Be @("test1")
        }

        It "disconnects from the sftp server" {
            $mockSFtp.DisconnectCalled | Should Be $true
        }
    }

    Context "when not connected" {
        $mockSFtp = New-Object MockSFtp
        $mockSFtp.IsConnected = $false
        Mock New-Object -MockWith { $mockSFtp }
        $files = Get-FromSFtp

        It "returns 0 files" {
            $files | Should BeNullOrEmpty
        }
    }

    Context "when an exception happens" {
        $mockSFtp = New-Object ThrowingMockSFtp
        Mock New-Object -MockWith { $mockSFtp }

        It "prints out the error to the user" {
            # I do not think this is a good test, but until
            # mocking of Write-Host can be done, this is all
            # that we can really do.
            { Get-FromSFtp } | Should Not Throw
        }
    }
}

Describe "Get-FromSFtp Integration" {
    It "returns the 2 default dir entries" {
        Get-FromSFtp | ForEach-Object { $_.Name } | Should Be ".", ".."
    }
}

Vagrantfile

# -*- mode: ruby -*-
# vi: set ft=ruby :

# Vagrantfile API/syntax version. Don't touch unless you know what you're doing!
VAGRANTFILE_API_VERSION = "2"

Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
  config.vm.box = "precise64"
  config.vm.box_url = "http://files.vagrantup.com/precise64.box"
  config.vm.network "forwarded_port", guest: 22, host: 22
end