How do you verify that the application continues to function?

Conducted comprehensive testing of the application, utilizing manual testing and automation.

Manual Testing:

• Exploratory Testing: Freely exploring the functionality to find non-obvious defects.
• Regression Testing: Checking previously tested functionality after making changes.
• End-to-End Testing: Testing user scenarios from start to finish.
• Performance Testing: Subjective assessment of interface responsiveness and load speed.

Automation Testing:

• Unit Tests: Checking the functionality of individual modules and functions (developed by developers).
• Integration Tests: Checking interaction between modules.
• UI Tests: Automating the verification of the user interface and execution of user scenarios. Used frameworks adapted to the application's stack (e.g., Selenium, Cypress, Playwright).

Example of an automated test using Selenium (Python):

from selenium import webdriver
from selenium.webdriver.common.by import By

# Initialize WebDriver
driver = webdriver.Chrome()

# Open the page
driver.get("http://example.com")

# Check the page title
assert "Example" in driver.title

# Find element by ID and interact with it
element = driver.find_element(By.ID, "some_element_id")
element.click()

# Verify element presence after action
assert driver.find_element(By.CLASS_NAME, "new_element_class")

# Close the browser
driver.quit()

• API Tests: Automating RESTful API checks using libraries (e.g., requests for Python, RestAssured for Java).

Example of an API test using requests (Python):

import requests

# Send GET request
response = requests.get("http://api.example.com/users")

# Check response status
assert response.status_code == 200

# Check response content
users = response.json()
assert isinstance(users, list)
assert len(users) > 0

# Check field in the first list item
assert "name" in users[0]

• Log and Metrics Monitoring: Monitoring server logs, performance metrics (CPU, RAM, network bandwidth) using monitoring systems (e.g., Grafana, Prometheus, ELK Stack).

Approach to Ensuring Continuous Functioning:

• CI/CD: Integrating automated tests into continuous integration/delivery pipelines for automatic test runs upon code changes.
• Regression Planning: Regular execution of a full regression test suite before releases.
• Production Environment Monitoring: Setting up alert systems to notify about failures or deviations in production.
• Post-deployment Testing: Quick tests on the production environment after successful deployment.

Thus, a combination of various testing types and automation, integrated into the development process, allows effective control and assurance of the application's functioning.