diff --git a/DSCResources/MSFT_xDNSServerAddress/MSFT_xDNSServerAddress.psm1 b/DSCResources/MSFT_xDNSServerAddress/MSFT_xDNSServerAddress.psm1
index a7bc13b6..294b5656 100644
--- a/DSCResources/MSFT_xDNSServerAddress/MSFT_xDNSServerAddress.psm1
+++ b/DSCResources/MSFT_xDNSServerAddress/MSFT_xDNSServerAddress.psm1
@@ -11,6 +11,7 @@
 ######################################################################################
 function Get-TargetResource
 {
+    [OutputType([System.Collections.Hashtable])]
     param
     (        
         [Parameter(Mandatory)]
@@ -21,8 +22,9 @@ function Get-TargetResource
         [ValidateNotNullOrEmpty()]
         [String]$InterfaceAlias,
 
+        [Parameter(Mandatory)]
         [ValidateSet("IPv4", "IPv6")]
-        [String]$AddressFamily = "IPv4"
+        [String]$AddressFamily
     )
     
     
@@ -52,8 +54,9 @@ function Set-TargetResource
         [ValidateNotNullOrEmpty()]
         [String]$InterfaceAlias,
 
+        [Parameter(Mandatory)]
         [ValidateSet("IPv4", "IPv6")]
-        [String]$AddressFamily = "IPv4"
+        [String]$AddressFamily
     )
 
     ValidateProperties @PSBoundParameters -Apply
@@ -65,6 +68,7 @@ function Set-TargetResource
 ######################################################################################
 function Test-TargetResource
 {
+    [OutputType([System.Boolean])]
     param
     (        
         [Parameter(Mandatory)]
@@ -75,8 +79,9 @@ function Test-TargetResource
         [ValidateNotNullOrEmpty()]
         [String]$InterfaceAlias,
 
+        [Parameter(Mandatory)]
         [ValidateSet("IPv4", "IPv6")]
-        [String]$AddressFamily = "IPv4"
+        [String]$AddressFamily
     )
 
     ValidateProperties @PSBoundParameters
@@ -99,6 +104,7 @@ function ValidateProperties
         [ValidateNotNullOrEmpty()]
         [String]$InterfaceAlias,
 
+        [Parameter(Mandatory)]
         [ValidateSet("IPv4", "IPv6")]
         [String]$AddressFamily,
 
diff --git a/DSCResources/MSFT_xDNSServerAddress/MSFT_xDNSServerAddress.schema.mof b/DSCResources/MSFT_xDNSServerAddress/MSFT_xDNSServerAddress.schema.mof
index 5431748b..53b31d67 100644
--- a/DSCResources/MSFT_xDNSServerAddress/MSFT_xDNSServerAddress.schema.mof
+++ b/DSCResources/MSFT_xDNSServerAddress/MSFT_xDNSServerAddress.schema.mof
@@ -1,7 +1,7 @@
-[ClassVersion("1.0.0"), FriendlyName("xDNSServerAddress")] 
-class MSFT_xDNSServerAddress : OMI_BaseResource
-{
-  [Required] string Address[];
-  [Key] string InterfaceAlias;
-  [Write,ValueMap{"IPv4", "IPv6"},Values{"IPv4", "IPv6"}] string AddressFamily;
-};
+[ClassVersion("1.0.0"), FriendlyName("xDNSServerAddress")] 
+class MSFT_xDNSServerAddress : OMI_BaseResource
+{
+  [Required] string Address[];
+  [Key] string InterfaceAlias;
+  [Key,Write,ValueMap{"IPv4", "IPv6"},Values{"IPv4", "IPv6"}] string AddressFamily;
+};
diff --git a/README.md b/README.md
index 7bfdb208..b0f6cb39 100644
--- a/README.md
+++ b/README.md
@@ -49,6 +49,10 @@ Please check out common DSC Resources [contributing guidelines](https://github.c
 
 ## Versions
 
+### Unreleased
+* Update to xDNSServerAddress to allow both IPv4 and IPv6 DNS addresses to be assigned to an
+  interface. xDNSServerAddress AddressFamily parameter has been changed to mandatory.
+
 ### 2.2.0.0
 * Changes in xFirewall resources to meet Test-xDscResource criteria
 
diff --git a/Tests/MSFT_xDNSServerAddress.Tests.ps1 b/Tests/MSFT_xDNSServerAddress.Tests.ps1
new file mode 100644
index 00000000..cd041370
--- /dev/null
+++ b/Tests/MSFT_xDNSServerAddress.Tests.ps1
@@ -0,0 +1,100 @@
+$here = Split-Path -Parent $MyInvocation.MyCommand.Path
+
+if (Get-Module MSFT_xDNSServerAddress -All)
+{
+    Get-Module MSFT_xDNSServerAddress -All | Remove-Module
+}
+
+Import-Module -Name $PSScriptRoot\..\DSCResources\MSFT_xDNSServerAddress -Force -DisableNameChecking
+
+InModuleScope MSFT_xDNSServerAddress {
+
+    Describe 'Get-TargetResource' {
+
+        #region Mocks
+        Mock Get-DnsClientServerAddress -MockWith {
+
+            [PSCustomObject]@{
+                ServerAddresses = '192.168.0.1'
+                InterfaceAlias = 'Ethernet'
+                AddressFamily = 'IPv4'
+            }
+        }
+        #endregion
+
+        Context 'comparing IPAddress' {
+            It 'should return true' {
+
+                $Splat = @{
+                    Address = '192.168.0.1'
+                    InterfaceAlias = 'Ethernet'
+                    AddressFamily = 'IPv4'
+                }
+                $Result = Get-TargetResource @Splat
+                $Result.IPAddress | Should Be $Splat.IPAddress
+            }
+        }
+    }
+
+
+    Describe 'ValidateProperties' {
+
+        #region Mocks
+        Mock Get-DnsClientServerAddress -MockWith {
+
+            [PSCustomObject]@{
+                ServerAddresses = '192.168.0.1'
+                InterfaceAlias = 'Ethernet'
+                AddressFamily = 'IPv4'
+            }
+        }
+
+        Mock Set-DnsClientServerAddress -MockWith {}
+        #endregion
+
+        Context 'invoking without -Apply switch' {
+
+            It 'should be $false' {
+                $Splat = @{
+                    Address = '10.0.0.2'
+                    InterfaceAlias = 'Ethernet'
+                    AddressFamily = 'IPv4'
+                }
+                $Result = ValidateProperties @Splat
+                $Result | Should Be $false
+            }
+
+            It 'should be $true' {
+                $Splat = @{
+                    Address = '192.168.0.1'
+                    InterfaceAlias = 'Ethernet'
+                    AddressFamily = 'IPv4'
+                }
+                $Result = ValidateProperties @Splat
+                $Result | Should Be $true
+            }
+
+            It 'should call Get-DnsClientServerAddress once' {
+                Assert-MockCalled -commandName Get-DnsClientServerAddress
+            }
+        }
+
+        Context 'invoking with -Apply switch' {
+
+            It 'should be $null' {
+                $Splat = @{
+                    Address = '10.0.0.2'
+                    InterfaceAlias = 'Ethernet'
+                    AddressFamily = 'IPv4'
+                }
+                $Result = ValidateProperties @Splat -Apply
+                $Result | Should BeNullOrEmpty
+            }
+
+            It 'should call all the mocks' {
+                Assert-MockCalled -commandName Get-DnsClientServerAddress
+                Assert-MockCalled -commandName Set-DnsClientServerAddress
+            }
+        }
+    }
+}