What are the best tools for web application testing and debugging?

I have used DevTools on countless occasions for debugging and some basic unit testing. As a frontend developer, they are extremely easy to incorporate in your debugging structure as it acts like a console output on the browser. On occasions, I have also known them to pose a security threat to web applications; especially when the styles are not coded properly. Ability to include dynamically typed code through the element tab of DevTools sometimes cause security issue to the original Document Object Model - DOM.

1) Browser DevTools: Built-in browser features for debugging and network monitoring. 2) Postman: API testing and documentation for REST and SOAP APIs. 3) Selenium: Open-source framework for web automation. 4) Cypress: JavaScript-based end-to-end testing with live reloading. 5) Jenkins: Automation server for CI/CD. 6) TestCafe: Cross-browser end-to-end testing framework. 7) Charles Proxy: Tool to debug web traffic. 8) Wireshark: Real-time network protocol analyzer. 9) Fiddler: Proxy tool for HTTP/HTTPS traffic inspection. 10) LogRocket: Session replay and performance monitoring. 11) VSCode: Code editor with debugging support. 12) BrowserStack: Cloud-based cross-browser testing. 13) New Relic: Monitoring and observability platform.

In my opinion, the testing frameworks are extremely powerful. They have the power to increase productivity for web applications while ensuring their robustness. I have encountered many engineers use it, and one of the best strategies I found is to delegate large end-to-end use cases to the automation. You can run them on a virtual machine while you ensure the quality using techniques like boundary value analysis simultaneously. The frameworks like Cypress, Playwright that support frontend programming languages are preferred as they are more reliable for dynamically changing content in the DOM structure.

Specifically the debugging features like "step over" and "evaluate expressions" have saved me countless hours. They allow you to evaluate a line (or lines) of code before the compiler reaches there, and in case, the line does not give you the expected output, you can skip over that line, and move forward to the next line of execution. With this strategy, you manually have to assist the automation script but it is still faster than the a few script failures before reaching the right one.

Developer Tools for Browsers is a blessing for debugging the associated code for easy catching errors/bugs. The following 3 crucial tabs to look out/work on: 1. Console Tab -- for any underlying messages or error codes (including stack traces in some cases) 2. Network Tab -- for identifying the trigger of any associated processes or APIs based on the browser events. If a back-end integration with APIs are involved, tools like Postman comes in handy too. 3. Source Tab -- when in combination with tools like Proxyman, Fiddler or Wireshark to actual trace and debug step by step code using breakpoints.

Recently, I have learnt that now Postman allows you to do performance testing as well. You can create an artificial load for the API of your choice, and see how it will perform with the size of load you are giving to it. As a full-stack software quality person, this definitely comes in handy.

Linting tools are helpful to developers of all skill levels. They are, however, particularly useful for newer developers. These tools not only help find issues with your code, but also can enhance the readability which can have a compounding efficiency when you consider how many times developers may need to review that code in the future.

Performance testing falls into two main categories: Front-end and back-end. For the back-end the biggest factors to de-risk are how quickly is each request served, and how many requests can be served in parallel before collapse. Load testing will pinpoint bottlenecks here. Front-end performance is tied to the end user experience. Since each user brings their own CPU, the challenge is less "how much traffic can we handle", and more "how quickly can the app become visible and usable?" Here, the main challenges are the power of the user's device, and the speed of their network. It can be helpful to run these tests on a slow CPU and slow network. If your app is fast on a 10 year old phone on a 3G network, you're in great shape for launch.

Effectively utilizing performance tools can assist web developers in elevating their solutions to the next level. Building an elegant user experience and effective backend code is certainly foundational, but when that solution clocks in at multiple seconds to load, you are going to find yourself communicating with unhappy stakeholders either up front or after your solution goes live and the performance is poor. For modern web where our website users start to wonder if something is broken after one to two seconds and have become used to near instant feedback and response times, performance should be a key consideration of any well built web experience.