Pester: Use variables in -ForEach data driven tests with rich content

Question

I write a module used for powershell-wrapping a commandline tool.

For my tests I had some variables defined in BeforeAll. Those vars should help in feeding the command with desired params and check them against the expected result, fi

BeforeAll {
   $PORead=@{
      Name = "Paul"
      Permission ="Read"
      Inheritance = "ThisFolderSubfoldersAndFiles"
   }

   $POReadExp="-bla bla (bla:bla;fra:fra;tra:tra)"
}

Now I want to use these in an it segment to feed the function and check the result, like:

It "checks result" -ForEach (
  @{Param=$PORead;Expected=$POReadExp}
) {
   $result=FunctionCall -Parameter1 $Param
   $result | Should -Be $Expected
}

Note: This is actually no working code - just to make clear what I want.

The problem is, that $Param and $Expected are $null, thus the current value of $PORead and $POReadExp are not assigned to $Param and $Expected. I made it easy to demonstrate the problem - in my code I use arrays in the -ForEach hash assigned to $Param and $Expected.

Using plain strings, there is no problem and everything works fine. I could use plain text and than use som switch construct to match my strings with the according variables from BeforeAll{}, but I thought there must be a more elegant way.

Using standard hashtables, the variable substition works fine.

I'd appreciate any idea.

---

To clarify some things:

The solution of Mark works somehow, but it needs the $PORead and $POReadExp to be set outside the BeforeAll-block (if you want to use -ForEach), or within the BeforeAll-block, but in that case you only can use one argument.

My plan was a bit different, so I'm making my point a bit clearer:

In the BeforeAll-block I wanted a bunch of definitions for params and outcomes

BeforeAll {
   $PORead = @{
   Name = "Paul"
   Permission ="Read"
   Inheritance = "ThisFolderSubfoldersAndFiles"

   $PODelete = @{
   Name = "Paul"
   Permission ="Delete"
   Inheritance = "ThisFolderOnly"
   }

   $POReadResult = "add parameters"
   $PODeleteResult = "delete parameters"
}

Now I want to test a whole bunch of combinations, feeding different combinations to the function and checking, if the combination of results match:

It "Test if all combinations works" -ForEach(
   @{FunctionParam=$PORead;Expected=$POReadExp}
   @{FunctionParam=$PORead,$PORead;Expected=$POReadExp,$POReadExp}
   @{FunctionParam=$PORead,$PODelete,$PORead,$PORead;Expected=$PORead,$PORead,$PORead,$PODelete}
) {
  $result = Function-Call -Param $FunctionParam
  $wanted = $expected -join(" ")
  $result | Should -Be $wanted
}

I can realize this by placing the definitions out of any block, but it feels wrong in terms of pester coding guidelines.

Greets Usul

Answer 1

The scopes for how to set test data with Pester v5 are quite confusing. What I've found is that anything you set in a BeforeAll or BeforeEach is available within the It . However if you want to set values to the -ForEach (or its alias -TestData ) you need to do it as part of or before the It , outside of the BeforeEach or BeforeAll .

As such I think your tests will work if you do this:

$PORead = @{
   Name = "Paul"
   Permission ="Read"
   Inheritance = "ThisFolderSubfoldersAndFiles"
}

$POReadExp = "-bla bla (bla:bla;fra:fra;tra:tra)"

It "checks result" -ForEach (
  @{Param=$PORead;Expected=$POReadExp}
) {
   $result=FunctionCall -Parameter1 $Param
   $result | Should -Be $Expected
}

Or alternatively:

BeforeAll {
   $PORead=@{
      Name = "Paul"
      Permission ="Read"
      Inheritance = "ThisFolderSubfoldersAndFiles"
   }

   $POReadExp="-bla bla (bla:bla;fra:fra;tra:tra)"
}

It "checks result" {
   $result = FunctionCall -Parameter1 $PORead
   $result | Should -Be $POReadExp
}