# Change body between predefined values **URL:** \ **Category:** Help Hub\ **Tags:** scripts, pre-request, request\ **Created:** [October 30, 2022, 12:23am UTC](https://community.postman.com/t/change-body-between-predefined-values/40601 "2022-10-30T00:23:43Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![shaga85](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@shaga85](https://community.postman.com/u/shaga85)\ **Post date:** [October 30, 2022, 12:23am UTC](https://community.postman.com/t/change-body-between-predefined-values/40601/1 "2022-10-30T00:23:43Z")
Hello there! Is there a way to change a body between predefined values everytime i run a POST request? For example: ```auto { "id": 11, "name": "Tutorialspoint", "username": "Test1", "email": "abc@gmail.com", } ``` i want the username to change between ´Test1, Test2, Test3ˋ everytime i run the request. Is it possible? ---
**Author:** ![w4dd325](https://sea2.discourse-cdn.com/getpostman/user_avatar/community.postman.com/w4dd325/32/12436_2.png) [@w4dd325](https://community.postman.com/u/w4dd325)\ **Post date:** [October 30, 2022, 9:57am UTC](https://community.postman.com/t/change-body-between-predefined-values/40601/2 "2022-10-30T09:57:39Z")
Hi @shaga85 You’re looking for ‘data driven testing’. Here are some resources: [https://learning.postman.com/docs/running-collections/working-with-data-files/](https://learning.postman.com/docs/running-collections/working-with-data-files/) > [@API Testing 'A Beginners View': Data-driven testing in Postman](https://community.postman.com/t/api-testing-a-beginners-view-data-driven-testing-in-postman/20302): > > Hi Everyone!!! Let’s check out some details about Data-Driven Testing with Postman using CSV and JSON files😊 Data-driven testing can be a very effective approach in testing an API against different data-sets. Postman supports CSV and JSON files to get data for the test scripts. The data-driven approach is useful when we need to execute a test with multiple sets of Data. Also, modifying or adding any data fields will just need updating the data files which is easier than going to test script and… [![](https://img.youtube.com/vi/fr7UpFNQbLw/maxresdefault.jpg "Data-driven testing using Postman") ](https://www.youtube.com/watch?v=fr7UpFNQbLw) ---
**Author:** ![shaga85](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@shaga85](https://community.postman.com/u/shaga85)\ **Post date:** [October 30, 2022, 10:21am UTC](https://community.postman.com/t/change-body-between-predefined-values/40601/3 "2022-10-30T10:21:35Z")
Nice, this will come in handy! Altough its not exactly what i need. I only want to have the request with one of the usernames (Test1 or Test2 or Test3), and not run alll 3 names like on the collection runner. Also i would like to only run this test without the need of the collection runner. Is this possible? ---
**Author:** ![w4dd325](https://sea2.discourse-cdn.com/getpostman/user_avatar/community.postman.com/w4dd325/32/12436_2.png) [@w4dd325](https://community.postman.com/u/w4dd325)\ **Post date:** [October 30, 2022, 10:46am UTC](https://community.postman.com/t/change-body-between-predefined-values/40601/4 "2022-10-30T10:46:48Z")
If its only 1 request you could set it as a variable and pass it in using the {{variable}} syntax. You could add a pre-req script to set the variable before the request is sent. How do you decide which user you want to send? ---
**Author:** ![shaga85](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@shaga85](https://community.postman.com/u/shaga85)\ **Post date:** [October 30, 2022, 11:04am UTC](https://community.postman.com/t/change-body-between-predefined-values/40601/5 "2022-10-30T11:04:00Z")
It can be random between those 3 usernames (Test1, Test2, Test3). I don’t need to have a specific order. How do I do that on the pre-request test? ---
**Author:** ![w4dd325](https://sea2.discourse-cdn.com/getpostman/user_avatar/community.postman.com/w4dd325/32/12436_2.png) [@w4dd325](https://community.postman.com/u/w4dd325)\ **Post date:** [October 30, 2022, 10:04pm UTC](https://community.postman.com/t/change-body-between-predefined-values/40601/6 "2022-10-30T22:04:45Z")
You could do something like this; ```auto //Create an array with all options let myList = ["User 1", "User 2", "User 3"]; //Generate a random number between 1 and array length let i = Math.floor(Math.random() * myList.length); //Output the value by using the random number as the array index console.log("Output variable = " + myList[i]); ``` ---
**Author:** ![michaelderekjones](https://sea2.discourse-cdn.com/getpostman/user_avatar/community.postman.com/michaelderekjones/32/14819_2.png) [@michaelderekjones](https://community.postman.com/u/michaelderekjones)\ **Post date:** [November 1, 2022, 2:26pm UTC](https://community.postman.com/t/change-body-between-predefined-values/40601/7 "2022-11-01T14:26:19Z")
The Lodash library is built-in to the Postman sandbox by default so you can use \_.sample. ```auto var randomString = _.sample(['Test1', 'Test2', 'Test3']); console.log(randomString); ``` > **[Postman JavaScript reference | Postman Learning Center](https://learning.postman.com/docs/writing-scripts/script-references/postman-sandbox-api-reference/#using-external-libraries)** > > Postman JavaScript reference: documentation for Postman, the collaboration platform for API development. Create better APIs—faster. > **[Lodash](https://lodash.com)** > > A JavaScript utility library delivering consistency, modularity, performance, & extras. ---
**Author:** ![danny-dainton](https://sea2.discourse-cdn.com/getpostman/user_avatar/community.postman.com/danny-dainton/32/29401_2.png) [@danny-dainton](https://community.postman.com/u/danny-dainton)\ **Post date:** [September 1, 2023, 11:09am UTC](https://community.postman.com/t/change-body-between-predefined-values/40601/8 "2023-09-01T11:09:07Z")
Closed on September 1, 2023, 11:09am UTC