Unit testing with MVVM Architecture

I am trying to create MVVM architecture with unit testing. I create MVVM architecture by flowing this link.

How I have to write unit testing for this I am very new to unit testing, see the code give below.

viewcontroller:

func initViewModel(){

    //code for updating activity indicator in the view.
    loginViewModelObj.updateLoadingStatus = { [weak self] () in
        DispatchQueue.main.async {
            let isLoading = self?.loginViewModelObj.isLoading ?? false
            if isLoading {
                Utils.showCustomisedActivityIndicator((self?.view)!, height: 35, width: 35)
            }else {
                Utils.HideActivityIndicator((self?.view)!)
            }
        }
    }


    loginViewModelObj.checkLoginType =  { [weak self] () in
        DispatchQueue.main.async {

            let LoginType = (self?.loginViewModelObj.shouldCheckLoginType)!

            if (LoginType == 0)
            {
                self?.verifyEmailView.isHidden = true
                self?.verifyPasswordView.isHidden = false
                self?.verifiedIdTextField.text = self?.loginViewModelObj.email
                self?.passwordTextField.text = ""

            }
        }
    }
    }

I am calling this in viewdidload and api calling is done under UIButton:

let paramDict   =   ["user_input":userIdTextField.text!] as [String : Any]
        let siginDict   =   ["variables" : paramDict]


        //call api method in the ViewModel
        loginViewModelObj.makeApiCall(paramsDict: siginDict as [String : AnyObject])

in view model, I am parsing the response using kvc and in view model I am doing the following code:

class LoginViewModel: NSObject {

var deafults = RewardsUserDefaults()


var checkLoginType : (() -> ())?




var shouldCheckLoginType :Int = -1
{
    didSet {
        self.checkLoginType?()
    }

}




override init() {
    super.init()
}



func makeApiCall(paramsDict : [String:AnyObject]){

    self.isLoading = true

    ApiCallManager.sharedManager.CallApiWithMethod(suffixUrl: “XXXXXXX", methodType: .post, joseToken: "", parameters: paramsDict as Dictionary<String,Any> as Dictionary<String, AnyObject>) { (result, error) in

        self.isLoading = false

        if error! == APICallsError.RequestSuccess {
            if let dataDict = result!["data"] as? [String:AnyObject]{

                if let userIdentityDict     =   dataDict["validateUserIdentity"] as? [String:AnyObject]{

                    if userIdentityDict["success"] as? Int == 1 {

                        let successObj = (LoginModel(response: Utils.getResultDictionary(result: result, error: error)))
                        self.email = successObj.email
                        self.shouldCheckLoginType = successObj.userLoginType


                        UserDefaults.standard.setValue(successObj.auth_token, forKey: "at")


                        return
                    }
            }
        }else{
            print("API Call failed")

        }
    }
}

This the correct way of creating MMVM architecture, if yes how to apply unit testing for viewmodel, else if it is wrong can please suggest when I did the wrong.