Automatic example testing

helptest.ps1

# command to be tested
$commandName = 'Get-Command'
# get all examples from the help
$examples = Get-Help $commandName -Examples

# make a describe block that will contain tests for this 
Describe "Examples from $commandName" {
  $examples.Examples.Example | foreach { 
    # examples have different format, 
    # at least the ones I used that MS provided
    # so you need to either standardize them,
    # or provide some hints about what to do
    # such as putting the code first
    # followed by 
    #   #output: the desired output

    # here I am simply taking the first line and removing 'PS C:\>' 
    # which makes some of the tests fail
    $example = $_.Code -replace "`n.*" -replace "PS C:\\>" 

    # for every example we want a single It block
    It "Example - $example" {
      # mock the tested command so we don't actually do anything
      # because it can be unsafe and we don't have the environment setup
      # (so the only thing we are testing is that the code is semantically
      # correct and provides all the needed params)
      Mock $commandName { 
        # I am returning true here,
        # but some of the examples drill down to the returned object
        # so in strict mode we would fail
        $true 
      }

      # here simply invoke the example
      $result = Invoke-Expression $example
      # and check that we got result from the mock
      $result | Should -BeTrue
    }
  }
}