diff --git a/Tests/Private/Invoke-ZertoRestRequest.Tests.ps1 b/Tests/Private/Invoke-ZertoRestRequest.Tests.ps1
index 984d682..ffcd1dc 100644
--- a/Tests/Private/Invoke-ZertoRestRequest.Tests.ps1
+++ b/Tests/Private/Invoke-ZertoRestRequest.Tests.ps1
@@ -1,17 +1,114 @@
-$filePath = (Split-Path -Parent $MyInvocation.MyCommand.Path) -replace 'Tests', 'ZertoApiWrapper'
-$fileName = (Split-Path -Leaf $MyInvocation.MyCommand.Path ) -replace '.Tests.', '.'
-$file = Get-ChildItem "$filePath\$fileName"
-. $file.FullName
+#Requires -Modules Pester
+$global:here = (Split-Path -Parent $MyInvocation.MyCommand.Path)
+$global:function = ((Split-Path -leaf $MyInvocation.MyCommand.Path).Split('.'))[0]
 
-Describe $file.BaseName -Tag Unit {
-    it "file should exist" {
-        $file.FullName | should exist
-    }
+Describe $global:function -Tag 'Unit', 'Source', 'Built' {
 
-    It "is valid Powershell (Has no script errors)" {
-        $contents = Get-Content -Path $file.FullName -ErrorAction Stop
-        $errors = $null
-        $null = [System.Management.Automation.PSParser]::Tokenize($contents, [ref]$errors)
-        $errors | Should -HaveCount 0
+    InModuleScope -ModuleName ZertoApiWrapper {
+        Mock -ModuleName ZertoApiWrapper -CommandName Invoke-RestMethod {
+            "Ran Command"
+        }
+
+        Context "$global:function::Parameter Unit Tests" {
+            $thisCommand = get-command Invoke-ZertoRestRequest
+            it "has a mandatory string parameter for the uri" {
+                $thisCommand | Should -HaveParameter uri -Mandatory -Type String
+            }
+
+            it "uri parameter cannot be null or empty" {
+                $thisParameter = $thisCommand.Parameters['uri']
+                $thisParameter.Attributes.Where{ $_ -is [ValidateNotNullOrEmpty] }.Count | Should Be 1
+            }
+
+            it "has a non-mandatory string parameter for the method" {
+                $thisCommand | Should -HaveParameter method -Not -Mandatory
+                $thisCommand | Should -HaveParameter method -Type String
+            }
+
+            it "method parameter can only be 'GET', 'POST', 'PUT', 'DELETE'" {
+                $thisParameter = $thisCommand.Parameters['method']
+                $thisParameter.Attributes.Where{ $_ -is [ValidateSet] }.Count | Should Be 1
+                $thisParameter.Attributes.Where{ $_ -is [ValidateSet] }.validValues -contains 'GET' | Should -BeTrue
+                $thisParameter.Attributes.Where{ $_ -is [ValidateSet] }.validValues -contains 'PUT' | Should -BeTrue
+                $thisParameter.Attributes.Where{ $_ -is [ValidateSet] }.validValues -contains 'POST' | Should -BeTrue
+                $thisParameter.Attributes.Where{ $_ -is [ValidateSet] }.validValues -contains 'DELETE' | Should -BeTrue
+                $thisParameter.Attributes.Where{ $_ -is [ValidateSet] }.validValues.Count | Should -Be 4
+            }
+
+            it "has a non-mandatory string parameter for the apiVersion, default 'v1'" {
+                $thisCommand | Should -HaveParameter apiVersion -Not -Mandatory
+                $thisCommand | Should -HaveParameter apiVersion -Type String
+                $thisCommand | Should -HaveParameter apiVersion -DefaultValue "v1"
+            }
+
+            it "apiVersion parameter cannot be null or empty" {
+                $thisParameter = $thisCommand.Parameters['apiVersion']
+                $thisParameter.Attributes.Where{ $_ -is [ValidateNotNullOrEmpty] }.Count | Should Be 1
+            }
+
+            it "has a non-mandatory string parameter for the body" {
+                $thisCommand | Should -HaveParameter body -Not -Mandatory
+                $thisCommand | Should -HaveParameter body -Type String
+            }
+
+            it "apiVersion parameter cannot be null or empty" {
+                $thisParameter = $thisCommand.Parameters['body']
+                $thisParameter.Attributes.Where{ $_ -is [ValidateNotNullOrEmpty] }.Count | Should Be 1
+            }
+
+            it "has a non-mandatory string parameter for the contentType" {
+                $thisCommand | Should -HaveParameter contentType -Not -Mandatory
+                $thisCommand | Should -HaveParameter contentType -Type String
+                $thisCommand | Should -HaveParameter contentType -DefaultValue "application/json"
+            }
+
+            it "apiVersion parameter cannot be null or empty" {
+                $thisParameter = $thisCommand.Parameters['contentType']
+                $thisParameter.Attributes.Where{ $_ -is [ValidateNotNullOrEmpty] }.Count | Should Be 1
+            }
+
+            it "has a non-mandatory PSCredential parameter for the credential" {
+                $thisCommand | Should -HaveParameter credential -Type PSCredential
+                $thisCommand | Should -HaveParameter credential -not -mandatory
+            }
+
+            it "has a non-mandatory switch parameter to ReturnHeaders" {
+                $thisCommand | Should -HaveParameter returnHeaders -Type Switch
+                $thisCommand | Should -HaveParameter returnHeaders -Not -Mandatory
+            }
+
+        }
+
+        Context "$global:function::Function Unit Tests" {
+            Mock -ModuleName ZertoApiWrapper -CommandName Invoke-RestMethod {
+                "Ran Command"
+            }
+
+            BeforeEach {
+                Set-Variable -Name zvmHeaders -Scope Script -Value (@{ "Accept" = "application/json" })
+                Set-Variable -Name zvmLastAction -Scope Script -Value $(Get-date).Ticks
+                Set-Variable -Name zvmServer -Scope Script -Value "192.168.1.100"
+                Set-Variable -Name zvmPort -Scope Script -Value 9669
+            }
+
+            it "runs when called" {
+                Invoke-ZertoRestRequest -uri "MyUri" | Should -Be "Ran Command"
+            }
+
+            it "throws an error when zvmLastAction was more than 30 minutes ago" {
+                Set-Variable -Name zvmLastAction -Scope Script -Value $(Get-date).AddMinutes(-31).Ticks
+                { Invoke-ZertoRestRequest -uri "MyUri" } | Should Throw
+            }
+
+            it "throws an error when the zvmServer variable does not exist" {
+                Remove-Variable -Name zvmServer -Scope Script
+                { Invoke-ZertoRestRequest -uri "MyUri" } | Should Throw
+            }
+
+            Assert-MockCalled -CommandName Invoke-RestMethod -ModuleName ZertoApiWrapper -Exactly 1
+        }
     }
-}
\ No newline at end of file
+}
+
+Remove-Variable -Name function -Scope Global
+Remove-Variable -Name here -Scope Global