PowerShell Pester testing best practices based on Pester v5 conventions

# PowerShell Pester v5 Testing Guidelines

This guide provides PowerShell-specific instructions for creating automated tests using PowerShell Pester v5 module. Follow PowerShell cmdlet development guidelines in [powershell.instructions.md](./powershell.instructions.md) for general PowerShell scripting best practices.

## File Naming and Structure

- **File Convention:** Use `*.Tests.ps1` naming pattern
- **Placement:** Place test files next to tested code or in dedicated test directories
- **Import Pattern:** Use `BeforeAll { . $PSScriptRoot/FunctionName.ps1 }` to import tested functions
- **No Direct Code:** Put ALL code inside Pester blocks (`BeforeAll`, `Describe`, `Context`, `It`, etc.)

## Test Structure Hierarchy

```powershell
BeforeAll { # Import tested functions }
Describe 'FunctionName' {
    Context 'When condition' {
        BeforeAll { # Setup for context }
        It 'Should behavior' { # Individual test }
        AfterAll { # Cleanup for context }
    }
}
```

## Core Keywords