The Katalon Blog

Frontend Testing: A Complete Guide

Written by Hy Nguyen | Jan 6, 2025 7:52:14 AM

Imagine visiting your favorite e-commerce website, and right as you're about to click that “Buy Now” button, the page crashes. Frustrating, right? Now, imagine that happening to thousands of users. Not only is it bad for business, but it also leaves a terrible impression.

That’s why Frontend Testing is essential. It ensures that users get a seamless, bug-free experience.

What is Frontend Testing?

Frontend testing is the process of testing the visual and interactive elements of a web application to ensure they function correctly across different browsers, devices, and screen sizes.

In simple terms, it’s about testing everything the user sees and interacts with.

Here’s what gets tested in the frontend:

  • Buttons, links, and forms
  • Navigation menus
  • Images, fonts, and colors
  • Responsive design
  • Browser compatibility

Want to try frontend testing? Simply go to any website and try messing with it. As a user, using and interacting with a website is already doing frontend testing!

Frontend Testing vs Backend Testing

The frontend and the backend together makes up the web infrastructure.

The frontend is the user interface. It is everything that users see and directly interact with in a website.

The backend is the server side of the application. It is where all of the behind-the-scene processes happen.

To test any of them is to test if they fulfill their roles as expected.

Here's a simple comparing the activities of frontend testing vs backend testing:

Aspect

Frontend Testing

Backend Testing

Focus

Testing the user interface (UI) and user experience

Testing the server, database, and APIs

Goal

Ensure the app looks and works correctly for users

Ensure data processing, logic, and integrations work correctly

Common Tests

UI testing, functionality testing, usability testing

API testing, database testing, server validation

Tools

Selenium, Katalon Studio, Cypress

Postman, SoapUI, Katalon Studio (API tests)

Example

Checking if a login button works and looks good

Checking if the login request sends valid credentials to the server

Main Challenges

Handling various browsers, devices, and screen sizes

Ensuring data integrity, performance, and security

Benefits of Frontend Testing

Frontend testing brings a wide range of benefits:

  • Better UX: The frontend is the very first thing your users see and also the place that they interact with your application. A good frontend translates to good User Experience, which ultimately impacts how they perceive your brand.
  • Consistent design: Frontend testing is also about keeping your branding and design elements uniform across the entire app. It creates a polished and professional look.
  • Improved accessibility: For users who face physical challenges, the frontend must provide special tools for them to navigate around (such as dictation, color-blind mode, contrast adjustment, etc). It ensures that your app is user-friendly and inclusive.

Types of Frontend Testing

There are 6 major ways to categorize testing types:

  • By Application Type: Group tests by the type of software being tested (e.g., web, mobile, desktop).
  • By Application Layer: Group tests by layers like UI, backend, or API based on the three-tier architecture.
  • By Attribute: Group tests by specific characteristics, such as functionality, performance, or visual elements.
  • By Approach: Group tests by strategy, such as manual, automated, or AI-driven testing.
  • By Granularity: Group tests by scope, like unit tests for small components or end-to-end tests for the entire system.
  • By Testing Technique: Group tests by the method used, such as black-box, white-box, or gray-box testing.

Based on this, here are 5 popular frontend testing types:

1. Functional testing

Functional testing checks if the frontend features work as expected. It ensures buttons, forms, and links perform their intended actions.

Example Test Cases:

  1. Check if the login button works.
  2. Verify form input validation (e.g., email format).
  3. Test if navigation links open the right pages.

Best Practices:

  1. Focus on key user actions like login and checkout.
  2. Cover both valid and invalid inputs.

Read More: Test Case Design Techniques That You Should Know

2. Usability testing

Usability testing checks how easy and intuitive the frontend is for users. It ensures that users can navigate and interact with the app without confusion.

Example Test Cases:

  1. Verify that buttons and links are easy to find and click.
  2. Check if forms are clear and simple to fill out.
  3. Ensure error messages are helpful and easy to understand.

Best Practices:

  1. Keep navigation simple and consistent.
  2. Use clear labels and instructions.
  3. Test with real users to get feedback.

3. Cross-Browser Testing

Cross-browser testing ensures the frontend looks and works the same across different browsers and browser versions.

Example Test Cases:

  1. Check if the app works on Chrome, Firefox, Safari, and Edge.
  2. Verify that buttons, forms, and layouts display consistently.
  3. Ensure CSS and JavaScript behave correctly across browsers.

Best Practices:

  1. Prioritize popular browsers based on user data.
  2. Use automation testing tools for faster testing
  3. Regularly update tests to cover new browser versions.

4. Visual regression testing

Visual regression testing checks for unexpected changes in the UI after code updates. It ensures the app’s design and layout remain consistent.

Example Test Cases:

  1. Verify that the header and footer remain aligned after a code change.
  2. Check that font sizes, colors, and spacing remain consistent.
  3. Ensure images and icons are displayed correctly across pages.

Best Practices:

  1. Use screenshot comparison tools (e.g., Percy, Applitools).
  2. Run tests after every UI update.
  3. Focus on critical UI components like buttons, forms, and navigation.

5. Accessibility Testing

Accessibility testing ensures that the app is usable by people with disabilities. It checks for compliance with accessibility standards like WCAG.

Example Test Cases:

  1. Verify that all buttons and links can be accessed using a keyboard.
  2. Ensure images have descriptive alt text for screen readers.
  3. Check color contrast to ensure text is readable for users with visual impairments.

Best Practices:

  1. Use accessibility tools like Axe, Lighthouse, or Wave.
  2. Follow WCAG guidelines for inclusive design.
  3. Test with real assistive technologies (e.g., screen readers).

Automated Frontend Testing

Manual testing is great when it comes to frontend testing. All you have to do is launch the app and interact with it exactly how an end user would use it. However, manual testing can be tedious and time-consuming. That’s where automated frontend testing comes in.

Benefits of Automation:
✅ Saves time by running tests automatically.
✅ Increases test coverage.
✅ Reduces human error.

When it comes to automation, it is about writing automation scripts or leverage automation tools with script creation capabilities to help you. You can use:

  • Katalon Studio: A powerful, all-in-one test automation platform.
  • Selenium: One of the most popular open-source frameworks for web testing.
  • Cypress: Fast and reliable for modern web apps.

Pro Tip: Start small when automating frontend tests. Automate repetitive tasks, like login tests or form submissions, and gradually expand.

Frontend Testing Best Practices

To get the most out of frontend testing, follow these best practices:

  1. Test Early and Often: Run frontend tests at each development stage to catch UI and functionality bugs before they impact later phases.

  2. Use Real Devices for Testing: Validate your app on actual devices to catch performance, rendering, and compatibility issues that emulators might miss.

  3. Automate Where It Makes Sense: Automate repetitive tasks like regression and smoke tests to improve efficiency, but leave usability and exploratory testing to humans.

  4. Prioritize Cross-Browser and Cross-Device Testing: Ensure consistent performance and appearance by testing across popular browsers (Chrome, Safari, Firefox) and devices (desktop, mobile, tablet).

  5. Keep Tests Maintainable: Write reusable test scripts with clear naming conventions and modular functions to reduce maintenance time and avoid broken tests.