Add function Assert-Module (#14)

- Added the function `Assert-Module`.
- Updated the localized strings to have the unique id according to style
  guideline.

CHANGELOG.md

@@ -7,6 +7,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Added the function `Assert-Module`.
+
+### Changed
+
+- Updated the localized strings to have the unique id according to style
+  guideline.
+
 ## [0.3.0] - 2020-02-15
 
 ### Added

README.md

@@ -33,6 +33,14 @@ describing how to convert a DSC resource module to use DscResource.Common.
 Refer to the comment-based help for more information about these helper
 functions.
 
+### `Assert-Module`
+
+Assert if the specific module is available to be imported.
+
+```powershell
+Assert-Module -ModuleName 'DhcpServer'
+```
+
 ### `Get-LocalizedData`
 
 Gets language-specific data into scripts and functions based on the UI culture

source/Public/Assert-Module.ps1

@@ -0,0 +1,28 @@
+<#
+    .SYNOPSIS
+        Assert if the specific module is available to be imported.
+
+    .PARAMETER ModuleName
+        Specifies the name of the module to assert.
+
+    .EXAMPLE
+        Assert-Module -ModuleName 'DhcpServer'
+
+        This asserts that the module DhcpServer is available on the system.
+#>
+function Assert-Module
+{
+    [CmdletBinding()]
+    param
+    (
+        [Parameter(Mandatory = $true)]
+        [System.String]
+        $ModuleName
+    )
+
+    if (-not (Get-Module -Name $ModuleName -ListAvailable))
+    {
+        $errorMessage = $script:localizedData.ModuleNotFound -f $ModuleName
+        New-ObjectNotFoundException -Message $errorMessage
+    }
+}

source/en-US/DscResource.Common.psd1

@@ -1,11 +1,13 @@
+# Localized English (en-US) strings.
+
 ConvertFrom-StringData @'
-# English strings
-    PropertyTypeInvalidForDesiredValues = Property 'DesiredValues' must be either a [System.Collections.Hashtable], [CimInstance] or [PSBoundParametersDictionary]. The type detected was {0}.
-    PropertyTypeInvalidForValuesToCheck = If 'DesiredValues' is a CimInstance, then property 'ValuesToCheck' must contain a value.
-    PropertyValidationError = Expected to find an array value for property {0} in the current values, but it was either not present or was null. This has caused the test method to return false.
-    PropertiesDoesNotMatch = Found an array for property {0} in the current values, but this array does not match the desired state. Details of the changes are below.
-    PropertyThatDoesNotMatch = {0} - {1}
-    ValueOfTypeDoesNotMatch = {0} value for property {1} does not match. Current state is '{2}' and desired state is '{3}'.
-    UnableToCompareProperty = Unable to compare property {0} as the type {1} is not handled by the Test-DscParameterState cmdlet.
-    TestIsNanoServerOperatingSystemSku = OperatingSystemSKU {0} was returned by Win32_OperatingSystem when detecting if operating system is Nano Server.
+    PropertyTypeInvalidForDesiredValues = Property 'DesiredValues' must be either a [System.Collections.Hashtable], [CimInstance] or [PSBoundParametersDictionary]. The type detected was {0}. (DRC0001)
+    PropertyTypeInvalidForValuesToCheck = If 'DesiredValues' is a CimInstance, then property 'ValuesToCheck' must contain a value. (DRC0002)
+    PropertyValidationError = Expected to find an array value for property {0} in the current values, but it was either not present or was null. This has caused the test method to return false. (DRC0003)
+    PropertiesDoesNotMatch = Found an array for property {0} in the current values, but this array does not match the desired state. Details of the changes are below. (DRC0004)
+    PropertyThatDoesNotMatch = {0} - {1} (DRC0005)
+    ValueOfTypeDoesNotMatch = {0} value for property {1} does not match. Current state is '{2}' and desired state is '{3}'. (DRC0006)
+    UnableToCompareProperty = Unable to compare property {0} as the type {1} is not handled by the Test-DscParameterState cmdlet. (DRC0007)
+    TestIsNanoServerOperatingSystemSku = OperatingSystemSKU {0} was returned by Win32_OperatingSystem when detecting if operating system is Nano Server. (DRC0008)
+    ModuleNotFound = Please ensure that the PowerShell module '{0}' is installed. (DRC0009)
 '@

tests/Unit/Public/Assert-Module.Tests.ps1

@@ -0,0 +1,42 @@
+$ProjectPath = "$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 'Assert-Module' {
+        BeforeAll {
+            $testModuleName = 'TestModule'
+        }
+
+        Context 'When module is not installed' {
+            BeforeAll {
+                Mock -CommandName Get-Module
+            }
+
+            It 'Should throw the correct error' {
+                { Assert-Module -ModuleName $testModuleName -Verbose } | `
+                        Should -Throw ($script:localizedData.RoleNotFound -f $testModuleName)
+            }
+        }
+
+        Context 'When module is available' {
+            BeforeAll {
+                Mock -CommandName Import-Module
+                Mock -CommandName Get-Module -MockWith {
+                    return @{
+                        Name = $testModuleName
+                    }
+                }
+            }
+
+            It 'Should not throw an error' {
+                { Assert-Module -ModuleName $testModuleName -Verbose } | Should -Not -Throw
+            }
+        }
+    }
+}

tests/Unit/Public/New-InvalidArgumentException.Tests.ps1

@@ -5,7 +5,7 @@ $ProjectName = ((Get-ChildItem -Path $ProjectPath\*\*.psd1).Where{
     }).BaseName
 
 Import-Module $ProjectName -Force
-Describe 'DscResource.Common\New-InvalidArgumentException' {
+Describe 'New-InvalidArgumentException' {
     Context 'When calling with both the Message and ArgumentName parameter' {
         It 'Should throw the correct error' {
             $mockErrorMessage = 'Mocked error'
@@ -16,4 +16,4 @@ Describe 'DscResource.Common\New-InvalidArgumentException' {
     }
 
     Assert-VerifiableMock
-}
+}

tests/Unit/Public/New-ObjectNotFoundException.Tests.ps1

@@ -6,7 +6,7 @@ $ProjectName = ((Get-ChildItem -Path $ProjectPath\*\*.psd1).Where{
 
 Import-Module $ProjectName -Force
 
-Describe 'DscResource.Common\New-ObjectNotFoundException' {
+Describe 'New-ObjectNotFoundException' {
     Context 'When calling with Message parameter only' {
         It 'Should throw the correct error' {
             $mockErrorMessage = 'Mocked error'