It's very easy to exceed the rate limit. There is no way to simulate it but as you wish, just put the API call function in a loop and call more times than the rate.

This is a simply example using Node JS

for (var i=0; i<60; i++) {

    await send_sms()

}



async function send_sms(){

  try{

    var resp = await platform.post('/restapi/v1.0/account/~/extension/~/sms', {

             from: {phoneNumber: "fromNumber"},

             to: [{phoneNumber: "toNumber"}],

             text: "Hello from Node JS",

        })

    var jsonObj = await resp.json()

    console.log("SMS sent. Message status: " + jsonObj.messageStatus, jsonObj.id)

    var obj = resp.headers

    console.log(obj)

  }catch(e){

    console.log(await e.response.json())

  }

}

Please read this article to learn more about how to deal with API rate limit.