Mock vs stub comparison in Postman - Test Execution Compared

Test Overview

This test compares the behavior of a mock server and a stub in Postman. It verifies that the mock server returns the predefined response and the stub simulates a simple response for a dependent API call.

Test Code - PyTest

Postman

import requests

# URL of the Postman mock server
mock_url = "https://abc123.mock.pstmn.io/resource"

# URL of the stub endpoint (simulated with a simple local server or mock)
stub_url = "https://stub-server.local/api/v1/dependency"

# Test the mock server response
mock_response = requests.get(mock_url)
assert mock_response.status_code == 200, f"Expected 200 but got {mock_response.status_code}"
assert mock_response.json().get('message') == 'Mock response', "Mock response message mismatch"

# Test the stub response
stub_response = requests.get(stub_url)
assert stub_response.status_code == 200, f"Expected 200 but got {stub_response.status_code}"
assert stub_response.text == 'Stub response', "Stub response content mismatch"

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts	Test environment ready with mock server and stub endpoint URLs configured	-	PASS
2	Send GET request to Postman mock server URL	Mock server is running and ready to respond	Check if status code is 200	PASS
3	Verify mock server response JSON contains 'message' with value 'Mock response'	Response JSON received from mock server	Assert response JSON 'message' == 'Mock response'	PASS
4	Send GET request to stub endpoint URL	Stub endpoint is running and ready to respond	Check if status code is 200	PASS
5	Verify stub response text equals 'Stub response'	Response text received from stub endpoint	Assert response text == 'Stub response'	PASS
6	Test ends successfully with all assertions passed	Both mock and stub responses verified	-	PASS

Failure Scenario

Failing Condition: Mock server or stub endpoint returns unexpected status code or response content

Execution Trace Quiz - 3 Questions

What does the test verify about the Postman mock server?

A It modifies the request before sending

B It simulates a slow network response

C It returns a predefined JSON response with status 200

D It stores data permanently

Key Result

Always verify that mock servers and stubs return the exact expected responses to ensure your tests simulate real API behavior correctly.