Stress testing concepts in Testing Fundamentals - Test Execution Trace

Test Overview

This test simulates a stress test on a web application by sending a high number of requests to check if the system can handle extreme load without crashing. It verifies that the application remains responsive and does not return error status codes under stress.

Test Code - PyTest

Testing Fundamentals

import requests
import threading
import time

# URL to stress test
url = "https://example.com/api/data"

# Number of concurrent requests
num_requests = 50

# Store results
responses = []

# Function to send a GET request
def send_request():
    try:
        response = requests.get(url, timeout=5)
        responses.append(response.status_code)
    except requests.exceptions.RequestException:
        responses.append('error')

# Start time
start_time = time.time()

# Create and start threads
threads = []
for _ in range(num_requests):
    thread = threading.Thread(target=send_request)
    threads.append(thread)
    thread.start()

# Wait for all threads to complete
for thread in threads:
    thread.join()

# End time
end_time = time.time()

duration = end_time - start_time

# Assertions
assert all(code == 200 for code in responses), f"Some requests failed: {responses}"
assert duration < 10, f"Stress test took too long: {duration} seconds"

Execution Trace - 6 Steps

Step	Action	System State	Assertion	Result
1	Test starts	Test environment ready, target URL set to https://example.com/api/data	—	PASS
2	Creates 50 threads to send GET requests concurrently	50 threads running, each sending a request to the server	—	PASS
3	Waits for all threads to complete	All requests completed, responses collected	—	PASS
4	Checks all response status codes are 200	Responses array contains status codes from all requests	assert all(code == 200 for code in responses)	PASS
5	Checks total test duration is less than 10 seconds	Duration calculated from start to end of requests	assert duration < 10	PASS
6	Test ends successfully	System handled stress load without errors or delays	—	PASS

Failure Scenario

Failing Condition: One or more requests return a status code other than 200 or the test duration exceeds 10 seconds

Execution Trace Quiz - 3 Questions

What does the test verify about the server responses?

A Responses are slower than 10 seconds

B Responses contain at least one error

C All responses have status code 200

D Responses have status code 404

Key Result

Stress testing uses many simultaneous requests to check system limits and ensures the system remains stable and responsive under heavy load.

Practice

1. What is the main goal of stress testing in software testing?

easy

A. To verify the system's installation process

B. To check if the system meets all functional requirements

C. To test the system's user interface for usability

D. To push the system beyond its normal limits to find breaking points

Solution

1. Step 1: Understand the purpose of stress testing

   Stress testing is designed to push a system beyond normal operational capacity to see how it behaves under extreme conditions.

2. Step 2: Compare options with stress testing goal

   Only To push the system beyond its normal limits to find breaking points describes pushing the system beyond normal limits to find breaking points, which matches stress testing's main goal.

3. Final Answer:

   To push the system beyond its normal limits to find breaking points -> Option D

4. Quick Check:

   Stress testing = pushing limits [OK]

Hint: Stress testing means pushing beyond normal use [OK]

Common Mistakes:

• Confusing stress testing with functional testing
• Thinking stress testing checks UI or installation
• Assuming stress testing is about normal load only

2. Which of the following is the correct way to describe a stress test scenario?

easy

A. Testing the system with a load that exceeds its maximum capacity

B. Testing the system with normal expected user load

C. Testing only the system's database queries

D. Testing the system's response to a single user action

Solution

1. Step 1: Define stress test scenario

   A stress test scenario involves applying a load that is higher than the system's maximum expected capacity to observe failure points.

2. Step 2: Match options to definition

   Testing the system with a load that exceeds its maximum capacity correctly states testing with load exceeding maximum capacity, which fits stress testing. Other options describe normal load or unrelated tests.

3. Final Answer:

   Testing the system with a load that exceeds its maximum capacity -> Option A

4. Quick Check:

   Stress test = load beyond max [OK]

Hint: Stress test means load beyond max capacity [OK]

Common Mistakes:

• Choosing normal load as stress test
• Confusing stress test with functional or unit tests
• Ignoring the 'exceeds capacity' part

3. Consider this pseudo-code for a stress test:

for users in range(1000, 1100):
    simulate_login(users)
    simulate_data_request(users)
    check_response_time(users)

What is the main purpose of increasing users from 1000 to 1099 in this test?

medium

A. To check if the system crashes at 1000 users

B. To verify system functionality for exactly 1000 users

C. To test system behavior under gradually increasing load

D. To test only the login feature repeatedly

Solution

1. Step 1: Analyze the loop range and actions

   The loop increases user count from 1000 to 1099, simulating login and data requests for each user count, then checking response time.

2. Step 2: Understand the test goal

   This gradual increase tests how the system handles increasing load, which is typical in stress testing to find breaking points or performance degradation.

3. Final Answer:

   To test system behavior under gradually increasing load -> Option C

4. Quick Check:

   Increasing users = increasing load [OK]

Hint: Increasing users means testing load growth [OK]

Common Mistakes:

• Thinking test is only for exactly 1000 users
• Assuming test checks only login feature
• Ignoring the gradual increase aspect

4. A tester wrote this stress test code snippet:

for i in range(1000, 1100):
    simulate_login(i)
    simulate_data_request(i)
    check_response_time()

What is the main issue in this code?

medium

A. The check_response_time function is missing the user parameter

B. The loop range is incorrect for stress testing

C. The simulate_login function should be outside the loop

D. There is no issue; the code is correct

Solution

1. Step 1: Review function calls inside the loop

   The loop calls simulate_login(i) and simulate_data_request(i) with the user parameter i. However, check_response_time() is called without any parameter.

2. Step 2: Identify inconsistency

   Since response time likely depends on the user or request, missing the user parameter in check_response_time() is an error causing incorrect or failed measurement.

3. Final Answer:

   The check_response_time function is missing the user parameter -> Option A

4. Quick Check:

   Missing parameter in function call = bug [OK]

Hint: Check all function calls have needed parameters [OK]

Common Mistakes:

• Ignoring missing parameters in function calls
• Thinking loop range is wrong for stress testing
• Assuming functions should be outside the loop

5. You want to design a stress test for a web application that must handle up to 5000 users simultaneously. Which approach best fits stress testing principles?

hard

A. Test the system with 3000 users and assume it works for 5000

B. Gradually increase users from 1000 to 6000 while monitoring system response and failures

C. Run functional tests for 100 users repeatedly

D. Test only 5000 users once and check if the system crashes

Solution

1. Step 1: Understand stress testing for capacity limits

   Stress testing involves pushing the system beyond expected limits to find breaking points and observe behavior under extreme load.

2. Step 2: Evaluate options for best stress test design

   Gradually increase users from 1000 to 6000 while monitoring system response and failures gradually increases users beyond 5000 to 6000, monitoring response and failures, which aligns with stress testing goals. Other options either test only once, test fewer users, or do unrelated functional tests.

3. Final Answer:

   Gradually increase users from 1000 to 6000 while monitoring system response and failures -> Option B

4. Quick Check:

   Gradual increase beyond max = proper stress test [OK]

Hint: Increase load beyond max users gradually [OK]

Common Mistakes:

• Testing only once at max users
• Confusing stress test with functional test
• Assuming fewer users prove max capacity