Data Driven Testing in Postman

praveenaaraja23
Sep 16
3 min read

Data-driven testing means running the same API request multiple times with different sets of input data. Instead of manually changing values each time, we use a dataset to provide inputs automatically.

Why Use Data-Driven Testing?

No repetitive work – one test covers multiple scenarios.
More coverage – quickly test both positive and negative cases.
Saves time – a single request runs with multiple inputs in one go.

Postman provides two ways to pass sets of values to use in a collection run.

1. CSV File

2. JSON File

By selecting a JSON or CSV data file in the Collection Runner, we can test our requests with multiple different values as part of a single run.

Flow of Data Driven Testing:

1. Plan Your Test - Decide which API to test and which inputs will change.

2. Prepare Test Data

Create a CSV or JSON file.
Each row/object is a separate test case.

3. Parameterize Requests

Replace variable parts of the request (body, URL, headers) with placeholders like {{name}}.

4. Add Assertions

Define checks to validate responses automatically, like status codes or returned values.

5. Run Tests

Use Postman Collection Runner or Newman.
Each row/object runs as a separate iteration automatically.

6. Review Results

Check which tests passed or failed.
Analyze responses and generate reports if needed.

Data Driven Using CSV File:

1. Create a CSV file with the first row as headers (variable names) and each following row as a separate test case.

Here, Name, Email, Gender, and Status will be used as variables in Postman.

2. Use CSV variables in your POST request to https://gorest.co.in/public/v2/users In the body, reference the CSV headers inside double curly braces,

Postman will replace these placeholders with values from each row when you run the collection with the CSV.

Step 3: Validate Results in Scripts

1. Click on post response script and add assertions.

2. We can also save response values for later use.

This allows chaining requests, e.g., GET the user after POST.

Step 4: Run Collection with CSV File

1. Click on “…” next to collection name. Select on Run option.

2. Click on Select File and Upload your CSV file

3. Click Run.

Postman executes one iteration per row. Here as there are 4 set of data so 4 rows will run the request 4 times with their respective values.

Passing Data using Json File:

Step 1: JSON data file must start with an array ([...]), where each object ({...}) represents one test case. This Json file has 3 sets of data this we will pass to POST request

2. Parameterize variables in the POST request body using values from the JSON file (e.g., {{Name}}, {{Email}}) to send requests to https://gorest.co.in/public/v2/users.

The {{Name}}, {{Email}}, etc., are like blanks in a form. When Postman runs the test, it fills in each blank with the corresponding value from JSON file for that test.

Make sure the names match exactly, including capital letters, otherwise Postman won’t recognize them.

Step 3: Validate Results in Scripts tab

Click on post response script and add assertions.