Tuesday, December 02, 2014

Using Pester to validate DSC resources and configurations Part 2

Pester tests are like any other script. They grow and evolve over time. Here are a few more tests that I have testing my DSC resources and configurations that I recently added to my collection. 

Does every resource have a pester test?
This is probably one of the most important tests I have. Every resource should have a test, so why not test for that?

describe "DSCResources located in $PSScriptRoot\DSCResources" {

  foreach($Resource in $ResourceList)
    context $Resource.name {

      it "Has a pester test" {

        ($Resource.fullname + "\*.test.ps1") | should exist

If it is a standard resource, does it have the files it needs?
Each DSC resource needs to have two files in it. A *.psm1 file and a *.schema.mof file. I use the *.psm1 file as a quick way to identify standard resources differently than a composite resource. I know I will not ever reach a test condition that would cause once of these to fail, but I left it in place so I could change the logic later.

if(Test-Path ($Resource.fullname + "\$Resource.psm1"))

  it "Has a $Resource.schema.mof" {
    ($Resource.fullname + "\$Resource.schema.mof") | should exist
  it "Has a $Resource.psm1" {
    ($Resource.fullname + "\$Resource.psm1") | should exist

Does it pass Test-xDscSchema and Test-xDscResource tests?
I may as well test for these as part of my pester tests. They already validate a lot of things that are easy to overlook.

it "Passes Test-xDscSchema *.schema.mof" {
  Test-xDscSchema ($Resource.fullname + "\$Resource.schema.mof") | should be true
it "Passes Test-xDscResource" {
  Test-xDscResource $Resource.fullname | should be true

If it is a composite resource, does it have the required files?
A composite resource uses different files than a standard resource. It has a *.psd1 and a *.shema.psm1 that should exists. I don’t have any Test-xDSC functions for the composite resources so I add a few extra checks. I verify that the *.psd1 file references the *.psm1 and that the module does not throw any errors when dot sourcing it.

  it "Has a $Resource.schema.psm1" {
    ($Resource.fullname + "\$Resource.schema.psm1") | should exist
  it "Has a $Resource.psd1" {
    ($Resource.fullname + "\$Resource.psd1") | should exist
  it "Has a psd1 that loads the schema.psm1" {
    ($Resource.fullname + "\$Resource.psd1") | should contain "$Resource.schema.psm1"
  it "dot-sourcing should not throw an error" {
    $path = ($Resource.fullname + "\$Resource.schema.psm1")
    { Invoke-expression (Get-Content $path -raw) } | should not throw

I hope you find this examples useful. If you want to see more, take a look at part 1.