https://github.com/guitarrapc/GraniResource/tree/master/DSCResources/Grani_CredentialManager

Absent_AdministratorAccount.ps1

configuration Absent_PsDscRunAsCredential
{
    Import-DscResource -Modulename GraniResource
    Node localhost
    {
        cCredentialManager Absent
        {
            InstanceIdentifier = $Node.InstanceIdentifier
            Ensure = $Node.Ensure
            Target = $Node.Target
            PsDscRunAsCredential = $Node.PsDscRunAsCredential
        }
    }
}

$configurationData = @{
    AllNodes = @(
        @{
            NodeName = "localhost"
            PSDscAllowPlainTextPassword = $true
            InstanceIdentifier = "JustAnIdentifierToKeepUnique"
            Ensure = "Absent"
            Target = "DesiredTargetName"
            PsDscRunAsCredential = New-Object PSCredential ("administrator", ("SuperExcellntPassword____????1111" | ConvertTo-SecureString -Force -AsPlainText))
        }
    )
}

Absent_PsDscRunAsCredential -ConfigurationData $configurationData

Present_AdministratorAccount.ps1

configuration Present_PsDscRunAsCredential
{
    Import-DscResource -Modulename GraniResource
    Node localhost
    {
        cCredentialManager Present
        {
            InstanceIdentifier = $Node.InstanceIdentifier
            Ensure = $Node.Ensure
            Target = $Node.Target
            Credential = $Node.Credential
            PsDscRunAsCredential = $Node.PsDscRunAsCredential
        }
    }
}

$configurationData = @{
    AllNodes = @(
        @{
            NodeName = "localhost"
            PSDscAllowPlainTextPassword = $true
            InstanceIdentifier = "JustAnIdentifierToKeepUnique"
            Ensure = "Present"
            Target = "DesiredTargetName"
            Credential = New-Object PSCredential ("PesterTestDummy", ("PesterTestPassword" | ConvertTo-SecureString -Force -AsPlainText))
            PsDscRunAsCredential = New-Object PSCredential ("administrator", ("SuperExcellntPassword____????1111" | ConvertTo-SecureString -Force -AsPlainText))
        }
    )
}

Present_PsDscRunAsCredential -ConfigurationData $configurationData