Skip to content
Postman API Testing Tips

How To Use Postman To Set Key And Value

API Testing Blog

Setting Key-Value Pairs in Postman for API Testing

Postman is a powerful tool for API testing, and one of its key features is the ability to manage and send data with key-value pairs. This is essential for many API interactions, allowing you to send parameters, headers, and even entire request bodies in a structured format. Here’s a comprehensive guide on how to set key-value pairs in Postman, including practical examples.

1. Setting Key-Value Pairs in Request Headers

Request headers are useful for providing additional information about the request, such as authentication tokens, content types, and caching preferences.

  • Open a new request: Click the “New” button and choose “Request” to create a new request in Postman.

  • Set the URL: In the request builder, enter the API endpoint you want to test in the “Enter request URL” field.

  • Navigate to the “Headers” tab: Click the “Headers” tab in the request builder.

  • Add key-value pairs:

    • Click the “Add key” button or simply start typing a new key in the “Key” field.
    • Enter the corresponding value in the “Value” field.

Example:

Let’s say you need to set an Authorization header for a request requiring authentication.

  • Key: Authorization
  • Value: Bearer [your_access_token]

Sample Code:

{
  "Authorization": "Bearer your_access_token"
}

2. Setting Key-Value Pairs in Request Parameters

Request parameters are used to pass data along with the URL, modifying the request’s behavior or fetching specific data.

  • Open a new request: Create a new request as described in step 1.

  • Select the “Params” tab: Click the “Params” tab in the request builder.

  • Add key-value pairs:

    • Click the “Add param” button or type the key and value directly into the input fields.
    • Enter the parameter name in the “Key” field and the corresponding value in the “Value” field.

Example:

Let’s say you’re making a request to a /products endpoint to retrieve products matching specific criteria.

  • Key: category
  • Value: electronics

Sample Code:

{
  "category": "electronics"
}

3. Setting Key-Value Pairs in Request Body (JSON)

For requests where you need to send structured data, like when creating or updating resources, you’ll often use a JSON request body.

  • Open a new request: Create a new request as described in step 1.

  • Set the “Body” tab: Click the “Body” tab in the request builder.

  • Choose “raw” and select “JSON” from the dropdown menu: In the “Body” section, choose “raw” as the body type and select “JSON” from the dropdown menu.

  • Add key-value pairs:

    • Type your JSON code directly into the body field. In JSON, key-value pairs are enclosed in curly braces ({}), keys are strings enclosed in double quotes (""), and values can be of various data types (strings, numbers, booleans, arrays, etc.).

Example:

Consider creating a new user with the following data:

{
  "firstName": "John",
  "lastName": "Doe",
  "email": "john.doe@example.com"
}

4. Dynamic Key-Value Pairs Using Variables

Postman allows you to store values in variables and reference them when setting key-value pairs. This provides flexibility, allowing you to easily update your tests and automate data retrieval.

  • Create a new variable: Go to the Postman environment and click “Add a variable” to create a new variable.

    • Key: The variable name (e.g., apiKey).
    • Value: The value you want to store (e.g., your_api_key).

  • Reference the variable:

    • In any of the key-value pair fields we discussed earlier (headers, parameters, or body), type {{apiKey}} (replace apiKey with your variable name) to reference the corresponding variable.

Example:

  • Using a variable baseUrl to make requests to different environments:
{
  "url": "{{baseUrl}}/products"
}

5. Setting Key-Value Pairs with Collections

Postman’s collections provide a structured way to organize API requests and related data. Collections support variables and environments, making them ideal for managing complex sets of requests.

  • Create a new collection: Click the “New” button and choose “Collection” to create a new collection.
  • Add a request: Add a request to your collection as described in steps 1-4.
  • Set variables in the collection:
    • Click on the collection name in the left sidebar to open the collection settings.
    • Click the “Variables” tab and add key-value pairs representing variables specific to this collection.
  • Reference variables: Use the {{variable_name}} notation within your requests to pull in the values from the collection’s variables.

6. Setting Key-Value Pairs in Tests

While setting key-value pairs in request definition is crucial, Postman’s test scripts let you manipulate and verify data dynamically.

  • Create a test script: In the “Test” tab of your request, write JavaScript code using Postman’s built-in assertions and functions.
pm.test("Status code is 200", function () {
    pm.response.to.have.status(200);
});


// Extract a value from the response body
let userId = pm.response.json().id;


// Set a new variable
pm.environment.set("userId", userId);


// Use the variable for future requests
pm.sendRequest("{{baseUrl}}/users/{{userId}}");

This example demonstrates how to access response data, set variables within the test, and use them for subsequent requests within the same collection.

By mastering these techniques for setting key-value pairs in Postman, you’ll unlock the full power of this tool for API testing, enabling you to send complex requests, verify data integrity, and build robust automation workflows.

API Testing Blog