Load testing basics (Postman) - Build an Automation Script

Perform a basic load test on a REST API endpoint using Postman

Preconditions (3)

Step 1: Open Postman and create a new collection named 'Load Test Collection'

Step 2: Add a new GET request to the collection with the URL https://api.example.com/data

Step 3: Save the request

Step 4: Open the Postman Collection Runner

Step 5: Select the 'Load Test Collection'

Step 6: Set the number of iterations to 50

Step 7: Set the delay between requests to 0 ms

Step 8: Start the run

Step 9: Observe the results summary after completion

✅ Expected Result: All 50 requests complete successfully with status code 200, and the average response time is within acceptable limits (e.g., less than 500 ms)

Automation Requirements - Postman Collection Runner with built-in scripting

Assertions Needed:

Verify each response status code is 200

Verify response time is less than 500 ms for each request

Best Practices:

Use Postman test scripts to assert response status and time

Use Collection Runner to simulate multiple requests

Avoid hardcoding URLs inside test scripts; use variables

Keep delay between requests minimal for load testing

Analyze run summary for failures and response times

Automated Solution

Postman

pm.test('Status code is 200', () => {
    pm.response.to.have.status(200);
});

pm.test('Response time is less than 500ms', () => {
    pm.expect(pm.response.responseTime).to.be.below(500);
});

The test script uses Postman's pm.test function to create two checks for each request.

First, it verifies the HTTP status code is 200, meaning the request was successful.

Second, it checks that the response time is below 500 milliseconds to ensure the API performs well under load.

These scripts run automatically for each request during the Collection Runner execution, allowing us to validate all 50 iterations.

Common Mistakes - 3 Pitfalls

{'mistake': 'Not adding assertions in the test script', 'why_bad': "Without assertions, the test run won't verify if responses are correct or fast enough, missing failures.", 'correct_approach': 'Always add assertions for status code and response time in Postman test scripts.'}

Setting a high delay between requests during load testing

Hardcoding the API URL inside test scripts instead of using variables

Bonus Challenge

Now add data-driven testing by running the load test with 3 different API endpoints

Show Hint

Practice

1. What is the main purpose of load testing in Postman?

easy

A. To check how many users the app can handle at the same time

B. To find syntax errors in API requests

C. To test the UI responsiveness of the app

D. To verify database schema correctness

Solution

1. Step 1: Understand load testing goal

   Load testing is about simulating many users to see how the app performs under stress.

2. Step 2: Match with Postman usage

   Postman can send multiple requests to simulate users, so it helps check app capacity.

3. Final Answer:

   To check how many users the app can handle at the same time -> Option A

4. Quick Check:

   Load testing = user capacity check [OK]

Hint: Load testing = many users at once [OK]

Common Mistakes:

• Confusing load testing with syntax checking
• Thinking load testing checks UI only
• Mixing load testing with database tests

2. Which Postman feature allows you to run multiple requests repeatedly for load testing?

easy

A. Postman Runner

B. Postman Console

C. Postman Monitor

D. Postman Collection Editor

Solution

1. Step 1: Identify Postman features for running requests

   Postman Runner lets you run a collection of requests multiple times.

2. Step 2: Match feature to load testing

   Running requests repeatedly simulates load, so Runner is the correct tool.

3. Final Answer:

   Postman Runner -> Option A

4. Quick Check:

   Repeated runs = Postman Runner [OK]

Hint: Use Runner to repeat requests [OK]

Common Mistakes:

• Choosing Console which is for debugging
• Confusing Monitor with scheduled tests
• Thinking Collection Editor runs requests

3. Consider this Postman Runner setup: you run 100 iterations with 10 requests each. How many total requests are sent?

medium

A. 100

B. 10

C. 1000

D. 110

Solution

1. Step 1: Understand iterations and requests per iteration

   Each iteration runs 10 requests, and there are 100 iterations total.

2. Step 2: Calculate total requests

   Total requests = 100 iterations * 10 requests = 1000 requests.

3. Final Answer:

   1000 -> Option C

4. Quick Check:

   100 x 10 = 1000 [OK]

Hint: Multiply iterations by requests per iteration [OK]

Common Mistakes:

• Adding instead of multiplying
• Confusing iterations with requests
• Ignoring requests per iteration

4. You tried to run a load test in Postman Runner but only one request was sent repeatedly instead of the whole collection. What is the likely mistake?

medium

A. You forgot to save the collection

B. You selected a single request instead of the full collection

C. You used Monitor instead of Runner

D. You set iterations to 1

Solution

1. Step 1: Analyze the problem

   Only one request runs repeatedly, not the whole collection.

2. Step 2: Identify cause

   This happens if you run a single request in Runner instead of the entire collection.

3. Final Answer:

   You selected a single request instead of the full collection -> Option B

4. Quick Check:

   Single request run = wrong selection [OK]

Hint: Always select full collection for load test [OK]

Common Mistakes:

• Thinking iterations = 1 causes this
• Confusing Monitor with Runner
• Assuming saving fixes request selection

5. You want to perform a heavy load test beyond Postman's Runner limits. Which approach is best?

hard

A. Increase iterations in Postman Runner to 10,000

B. Use Postman Console to debug requests

C. Run Postman Monitor continuously for 24 hours

D. Use Newman in combination with a load testing tool like Apache JMeter

Solution

1. Step 1: Understand Postman Runner limits

   Postman Runner is good for basic load but not for very heavy or distributed load testing.

2. Step 2: Identify best heavy load testing method

   Newman can run collections from command line and can be integrated with tools like JMeter for heavy load.

3. Final Answer:

   Use Newman in combination with a load testing tool like Apache JMeter -> Option D

4. Quick Check:

   Heavy load = Newman + load tool [OK]

Hint: Combine Newman with load tools for heavy tests [OK]

Common Mistakes:

• Trying to increase Runner iterations too high
• Using Monitor for load testing
• Using Console for load testing