Generate data for a Postman request

24 November 2020

Updated: 03 September 2023

When making requests with Postman to test an API it is often useful to have generated data, for example when creating users in a backend system you may want the ability to get custom user data

The method we will use to do this is by setting Postman environment variables in the Pre-request Script of a Postman request

Firstly, we can write some basic logging in the Pre-request script section on Postman and view the result in the Postman console:

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const name = 'Nabeel'
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console.log(`Hello ${name}`)

Additionally, postman gives us some functions to set and get environment variables, so we can set the name as an environment variable like so:

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const name = 'Nabeel'
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pm.environment.set('name', name)

And log it like so:

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console.log(pm.environment.get('name'))

Aditionally, we can make HTTP Requests using pm.sendRequest which then takes a callback for what we want to do after the request, we can use the randomuser api to get a user:

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pm.sendRequest('https://randomuser.me/api/', (err, res) => {
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  const apiResponse = res.json()
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  // do more stuff
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})

Using this method, we can get some random user data and set it in the environment variables as follows:

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pm.sendRequest('https://randomuser.me/api/', (err, res) => {
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  const apiResponse = res.json()
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  const user = apiResponse.results[0]
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  const email = user.email
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  const firstName = user.name.first
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  const lastName = user.name.last
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  pm.environment.set('email', email)
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  pm.environment.set('firstName', firstName)
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  pm.environment.set('lastName', lastName)
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})

We can then use this in our request body using Postman’s {\{}\} syntax. If we were making a JSON request, our body would look something like this:

POST: https://my-api.com/users

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{
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  "email": "{{email}}",
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  "firstName": "{{firstName}}",
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  "lastName": "{{lastName}}"
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}

Postman will then populate the slots from the environment variables that we set automatically when making the request