? Data-Driven Testing in Postman

? Quick Overview

Data-driven testing in Postman allows you to run the same API request multiple times using different sets of input data. This is commonly achieved using external data files such as CSV and JSON, making your API tests scalable, reusable, and efficient.

? Key Concepts

Collection Runner executes requests using external data files
Variables are dynamically replaced per iteration
Supports CSV and JSON formats
Ideal for bulk testing and validation

? Syntax / Theory

Postman replaces variables like {{variableName}} with values from each row (CSV) or object (JSON) during execution.

? Code Example(s)

? View Code Example

// Access CSV or JSON data variable in Postman
let username = pm.iterationData.get("username");
let password = pm.iterationData.get("password");

pm.environment.set("user", username);
pm.environment.set("pass", password);

? Live Output / Explanation

? What Happens?

For each iteration, Postman injects a new username and password into the request. The same API endpoint is tested repeatedly with different data sets.

? Interactive Example (CSV Structure)

? View Code Example

// Example CSV file structure
username,password
admin,admin123
user1,pass123
user2,pass456

? JSON Data File Example

? View Code Example

// Example JSON data for Postman Runner
[
  {
    "username": "admin",
    "password": "admin123"
  },
  {
    "username": "user1",
    "password": "pass123"
  }
]

? Interactive Simulator: Variable Replacer

Edit the data below and click "Run Runner" to see how Postman replaces variables.

1. Request URL (with variables)

2. CSV Data Source

Waiting for execution...

? Use Cases

Login API testing with multiple users
Bulk data validation
Regression testing with varied inputs
Negative testing scenarios

✅ Tips & Best Practices

Keep variable names consistent with data headers
Use JSON for complex nested data
Validate responses using tests per iteration
Store sensitive data in environments

? Try It Yourself

Create a login API request using variables
Prepare a CSV file with 3 users
Run the collection using Collection Runner
Add assertions for response status and body