Added cmdlet Get-ComputerName (#60)

- Added cmdlet `Get-ComputerName` which can be used to returns the computer
  name cross-plattform. The variable `$env:COMPUTERNAME` does not exist
  cross-platform which hinders development and testing on macOS and Linux.
  Instead this cmdlet can be used to get the computer name cross-plattform.

CHANGELOG.md

@@ -7,6 +7,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Added cmdlet `Get-ComputerName` which can be used to returns the computer
+  name cross-plattform. The variable `$env:COMPUTERNAME` does not exist
+  cross-platform which hinders development and testing on macOS and Linux.
+  Instead this cmdlet can be used to get the computer name cross-plattform.
+
 ## [0.10.0] - 2020-11-18
 
 ### Added

README.md

@@ -455,6 +455,35 @@ ConvertTo-HashTable -CimInstance $cimInstance
 This creates a array om CimInstances of the class name MSFT_KeyValuePair
 and passes it to ConvertTo-HashTable which returns a hashtable.
 
+### `Get-ComputerName`
+
+Returns the computer name cross-plattform. The variable `$env:COMPUTERNAME`
+does not exist cross-platform which hinders development and testing on
+macOS and Linux. Instead this cmdlet can be used to get the computer name
+cross-plattform.
+
+#### Syntax
+
+<!-- markdownlint-disable MD013 - Line length -->
+```plaintext
+Get-ComputerName [<CommonParameters>]
+```
+<!-- markdownlint-enable MD013 - Line length -->
+
+#### Outputs
+
+**System.String**
+
+#### Notes
+
+None.
+
+#### Example
+
+```powershell
+$computerName = Get-ComputerName
+```
+
 ### `Get-LocalizedData`
 
 Gets language-specific data into scripts and functions based on the UI culture

source/Public/Get-ComputerName.ps1

@@ -0,0 +1,37 @@
+<#
+    .SYNOPSIS
+        Returns the computer name cross-plattform.
+
+    .DESCRIPTION
+        The variable `$env:COMPUTERNAME` does not exist cross-platform which
+        hinders development and testing on macOS and Linux. Instead this cmdlet
+        can be used to get the computer name cross-plattform.
+
+    .EXAMPLE
+        Get-ComputerName
+
+        This example returns the computer name cross-plattform.
+#>
+function Get-ComputerName
+{
+    [CmdletBinding()]
+    [OutputType([System.String])]
+    param ()
+
+    $computerName = $null
+
+    if ($IsLinux -or $IsMacOs)
+    {
+        $computerName = hostname
+    }
+    else
+    {
+        <#
+            We could run 'hostname' on Windows too, but $env:COMPUTERNAME
+            is more widely used.
+        #>
+        $computerName = $env:COMPUTERNAME
+    }
+
+    return $computerName
+}

tests/Unit/Public/Get-ComputerName.Tests.ps1

@@ -0,0 +1,37 @@
+$ProjectPath = "$PSScriptRoot\..\..\.." | Convert-Path
+$ProjectName = ((Get-ChildItem -Path $ProjectPath\*\*.psd1).Where{
+        ($_.Directory.Name -match 'source|src' -or $_.Directory.Name -eq $_.BaseName) -and
+    $(try { Test-ModuleManifest -Path $_.FullName -ErrorAction Stop } catch { $false } )
+    }).BaseName
+
+
+Import-Module $ProjectName
+
+InModuleScope $ProjectName {
+    Describe 'Get-ComputerName' {
+        BeforeAll {
+            $mockComputerName = 'MyComputer'
+
+            if ($IsLinux -or $IsMacOs)
+            {
+                function hostname
+                {
+                }
+
+                Mock -CommandName 'hostname' -MockWith {
+                    return $mockComputerName
+                }
+            }
+            else
+            {
+                $mockComputerName = $env:COMPUTERNAME
+            }
+        }
+
+        Context 'When getting computer name' {
+            It 'Should return the correct computer name' {
+                Get-ComputerName | Should -Be $mockComputerName
+            }
+        }
+    }
+}