Run order and flow control in Postman - Build an Automation Script

Verify run order and flow control in Postman collection

Preconditions (4)

Step 1: Run the collection

Step 2: Observe that Request1 runs first

Step 3: Observe that Request2 runs second and sets the 'runNext' variable

Step 4: Observe that Request3 runs only if 'runNext' is 'true'

Step 5: If 'runNext' is 'false', Request3 should be skipped

✅ Expected Result: Request1 and Request2 always run in order. Request3 runs only if the 'runNext' variable is set to 'true' by Request2, demonstrating run order and flow control.

Automation Requirements - Postman Collection Runner with pm scripting

Assertions Needed:

Verify Request1 runs before Request2

Verify Request2 sets environment variable 'runNext'

Verify Request3 runs only if 'runNext' is 'true'

Verify Request3 is skipped if 'runNext' is 'false'

Best Practices:

Use pm.environment.set and pm.environment.get for variable control

Use pm.test for assertions

Use postman.setNextRequest() to control flow

Keep scripts simple and readable

Automated Solution

Postman

/* Request1 Tests */
pm.test('Request1 runs', function () {
    pm.expect(true).to.be.true;
});

/* Request2 Tests and flow control */
// In Tests tab of Request2
pm.test('Request2 runs and sets runNext', function () {
    pm.environment.set('runNext', 'true'); // Change to 'false' to test skipping
    pm.expect(pm.environment.get('runNext')).to.be.oneOf(['true', 'false']);
});

// Control flow
if (pm.environment.get('runNext') === 'true') {
    postman.setNextRequest('Request3');
} else {
    postman.setNextRequest(null); // Stops collection run
}

/* Request3 Tests */
pm.test('Request3 runs only if runNext is true', function () {
    pm.expect(pm.environment.get('runNext')).to.eql('true');
});

This script uses Postman test scripts to control the run order and flow.

In Request2, we set an environment variable runNext to 'true' or 'false'.

Then, using postman.setNextRequest(), we decide if Request3 should run.

If runNext is 'true', Request3 runs next; otherwise, the collection stops.

Assertions verify that each request runs in order and that flow control works as expected.

Common Mistakes - 4 Pitfalls

Not using postman.setNextRequest() to control flow

Setting environment variables in the wrong script tab

Using global variables instead of environment variables

Not clearing or resetting variables before collection run

Bonus Challenge

Now add data-driven testing by running the collection with three different values of 'runNext' ('true', 'false', 'true') and verify Request3 runs accordingly.

Show Hint

Practice

1. In Postman, what does pm.setNextRequest() do in a collection run?

easy

A. It sets which request runs next in the collection.

B. It stops the entire collection run immediately.

C. It restarts the current request.

D. It logs the response of the current request.

Solution

1. Step 1: Understand the purpose of pm.setNextRequest()

   This function controls the flow by specifying the next request to run in the collection.

2. Step 2: Compare other options

   Stopping the run is done by pm.setNextRequest(null), not this function. Restarting or logging are unrelated.

3. Final Answer:

   It sets which request runs next in the collection. -> Option A

4. Quick Check:

   Flow control = set next request [OK]

Hint: Remember: setNextRequest controls next request flow [OK]

Common Mistakes:

• Confusing pm.setNextRequest() with stopping the run
• Thinking it restarts the current request
• Assuming it logs data instead of controlling flow

2. Which of the following is the correct syntax to stop running any further requests in a Postman collection?

easy

A. pm.abortRun()

B. pm.setNextRequest('stop')

C. pm.stopCollection()

D. pm.setNextRequest(null)

Solution

1. Step 1: Identify the method to stop collection run

   Postman uses pm.setNextRequest(null) to stop running further requests.

2. Step 2: Verify other options

   Other options like pm.stopCollection() or pm.abortRun() do not exist in Postman scripting.

3. Final Answer:

   pm.setNextRequest(null) -> Option D

4. Quick Check:

   Stop run = setNextRequest(null) [OK]

Hint: Use null in setNextRequest to stop run [OK]

Common Mistakes:

• Using a string like 'stop' instead of null
• Assuming non-existent functions stop the run
• Confusing stopping with skipping requests

3. Consider this Postman test script inside a request named 'Request A':

if (pm.response.code === 200) {
  pm.setNextRequest('Request B');
} else {
  pm.setNextRequest(null);
}

What happens if the response code is 404?

medium

A. The collection run continues to 'Request B'.

B. An error is thrown and the run fails.

C. The collection run stops after 'Request A'.

D. The collection run restarts from the first request.

Solution

1. Step 1: Analyze the condition for response code 404

   Since 404 is not 200, the else block runs pm.setNextRequest(null).

2. Step 2: Understand effect of pm.setNextRequest(null)

   This stops the collection run immediately after the current request.

3. Final Answer:

   The collection run stops after 'Request A'. -> Option C

4. Quick Check:

   404 triggers stop = setNextRequest(null) [OK]

Hint: If condition false, setNextRequest(null) stops run [OK]

Common Mistakes:

• Assuming it continues to next request regardless
• Thinking it restarts the collection
• Believing an error is thrown automatically

4. You wrote this test script in Postman:

pm.setNextRequest('Request C');
pm.setNextRequest(null);

What is the effect on the collection run flow?

medium

A. The run jumps to 'Request C' and then stops.

B. The run stops immediately; 'Request C' is skipped.

C. The run ignores both commands and continues normally.

D. The run loops infinitely between requests.

Solution

1. Step 1: Understand order of pm.setNextRequest calls

   Only the last pm.setNextRequest() call takes effect in a single script execution.

2. Step 2: Analyze the last call pm.setNextRequest(null)

   This stops the collection run immediately, ignoring previous setNextRequest calls.

3. Final Answer:

   The run stops immediately; 'Request C' is skipped. -> Option B

4. Quick Check:

   Last setNextRequest call wins = null stops run [OK]

Hint: Last setNextRequest call controls flow [OK]

Common Mistakes:

• Thinking both calls run in sequence
• Assuming first call overrides last
• Believing it causes infinite loops

5. You want to run a Postman collection where:
- If 'Login' request succeeds (status 200), run 'GetData'.
- If 'Login' fails, stop the run.
- After 'GetData', always run 'Logout'.

Which sequence of pm.setNextRequest() calls in the 'Login' and 'GetData' test scripts achieves this flow?

hard

A. In 'Login': pm.setNextRequest('GetData') if 200 else pm.setNextRequest(null);In 'GetData': pm.setNextRequest('Logout')

B. In 'Login': pm.setNextRequest('Logout') always;In 'GetData': pm.setNextRequest(null)

C. In 'Login': pm.setNextRequest(null) always;In 'GetData': pm.setNextRequest('Logout')

D. In 'Login': pm.setNextRequest('GetData') always;In 'GetData': pm.setNextRequest(null)

Solution

1. Step 1: Control flow after 'Login'

   If status is 200, next request should be 'GetData'; else stop run with pm.setNextRequest(null).

2. Step 2: Control flow after 'GetData'

   Always run 'Logout' next, so pm.setNextRequest('Logout') is set in 'GetData' tests.

3. Final Answer:

   In 'Login': pm.setNextRequest('GetData') if 200 else pm.setNextRequest(null); In 'GetData': pm.setNextRequest('Logout') -> Option A

4. Quick Check:

   Conditional jump + final logout = In 'Login': pm.setNextRequest('GetData') if 200 else pm.setNextRequest(null);
   In 'GetData': pm.setNextRequest('Logout') [OK]

Hint: Use conditional setNextRequest in Login, fixed next in GetData [OK]

Common Mistakes:

• Setting wrong next request after Login
• Not stopping run on Login failure
• Skipping Logout after GetData