Pester for Connect-NetScaler

Question

Hey guys having trouble writing pester for this function. The function is down below. Here is a link of the code if you prefer looking on here. https://www.powershellgallery.com/packages/NetScaler/1.1.2/Content/Public%5CConnect-NetScaler.ps1

Describe 'Connect-NetScaler' {
            $Credential = New-Object PSCredential('username', (ConvertTo-SecureString -AsPlainText -Force 'password'))
            Context 'Successful Connection' {
                Mock Add-Member {
                    return @{
                        Endpoint = '10.111.33.3'
                        Scheme   = 'http'
                    }
                 }
                Mock New-Object {
                    return @{
                    Uri='http://10.111.33.3/nitro/v1';
                }
            }
                Mock ConvertTo-Json -ParameterFilter {
                    $InputObject -eq $Credential
                }
                Mock 'Invoke-RestMethod' {
                 #   $Uri | Should -BeExactly "fakename/config/login"
                   # $Credential | Should -BeOfType PSCredential
                    return [PSCustomObject]@{
                        severity = 'NONE'
                    }
                } -Verifiable
                It 'Should be able to connect'{
                    $result= Connect-NetScaler -IPAddress '10.111.33.3' -Credential $Credential
                    $result | Should -Be "Response:`n"
                }

            }
            Context 'UnSuccessful Connection' {
                Mock Add-Member {
                    return @{
                        Endpoint = '10.111.33.3'
                        Scheme   = 'http'
                    }
                 }
                Mock New-Object {
                    return @{
                    Uri='http://10.111.33.3/nitro/v1';
                }
            }
                Mock ConvertTo-Json -ParameterFilter {
                    $InputObject -eq $Credential
                }
                Mock 'Invoke-RestMethod' {
                 #   $Uri | Should -BeExactly "fakename/config/login"
                   # $Credential | Should -BeOfType PSCredential
                    return [PSCustomObject]@{
                        severity = 'ERROR'
                    }
                } -Verifiable
                It 'Should be able to connect'{
                    $result= Connect-NetScaler -IPAddress '10.111.33.3' -Credential $Credential
                    $result | Should -Throw "Error. See response: `n"
                }
            }
        } 

This is the code for the function. I am a beginner to pester so been having trouble figuring this out. Any help would be greatly appreciated!