As a software testing veteran with over 10 years of expertise validating web and mobile applications on real browsers and devices, I cannot stress enough the immense value of comprehensive front end testing.
In this complete guide straight from the trenches, I will equip you with everything there is to know about front end testing—from key concepts to preferred tools to best practices. My goal is to help you deliver flawless user experiences consistently across devices.
What is Front End Testing and Why It Matters
Front end testing focuses on validating the user interface and user experience of websites, web apps, and mobile apps. Rather than testing behind-the-scenes business logic, front end testing revolves around what users see and interact with directly.
More specifically, front end testing confirms:
- The visual appearance, responsiveness, speed, and behavior of the UI
- How the interface performs across different devices, browsers, operating systems
- The accessibility and ease-of-use of the front end
- The functionality of UI components like menus, forms, buttons, etc
The overarching goal is to identify any front end defects that could frustrate users and fail to meet standards. By confirming your app‘s interface and UX works flawlessly before launch, you prevent damaging your brand’s reputation and losing customers.
Consider that:
- 63% of mobile site visits are abandoned if pages take over 3 seconds to load. Slow front ends directly impact revenue.
- A study found a page speed improvement of just .1 seconds increased conversion rates by 7.7%.
- Up to 20% of mobile users will abandon a site that is not mobile-friendly and fails to render properly across devices.
- 52% of users state that a couple occurrences of a website not working as expected means they will stop visiting the site altogether.
As you can see from these surprising statistics, delivering quality front end experiences across the exponentially expanding matrix of devices and browsers is now an expectation rather than a nice-to-have.
The costs of inadequate front end testing manifest in the form of:
- Loss of customers, transactions, and long-term revenue
- Irreparable damage your brand’s reputation and trust
- Expensive rework to fix issues spotted late in the game
By identifying and resolving front end defects through comprehensive testing early on, you avoid preventable consequences down the line.
Now that you understand what front end testing entails and why it matters, let‘s explore popular techniques.
Types of Front End Testing
While all validating the front end, different testing types have unique focuses at various test levels.
Unit Testing
Unit testing involves testing individual modules, components, or functions in isolation outside of our greater systems. For front end code, this means verifying discrete UI pieces like buttons, menus, and dialogs work properly on their own.
Unit testing establishes confidence in base code quality so higher test levels have dependable foundations. Front end developers often utilize unit testing frameworks like Jest, Mocha, Jasmine during coding to catch issues early.
Integration Testing
Whereas unit tests validate individual components, integration testing verifies collections of modules and services interoperating correctly. Front end integration testing focuses checkmarks like:
- Menus, search forms, and carts exchanging data
- Synchronized front end behavior across components
- Navigation flows across pages
Catching integration defects early on prevents more severe downstream bugs that are costly to fix.
Functional Testing
Functional testing validates that front end features and UI elements work per specifications from end user perspectives. Rather than testing code integrity, functional testing analyzes whether functions meet requirements.
Example front end functional tests:
- Analyzing form validation
- Testing search filtering
- Checking menus and navigation
- Validating user input handling and error messages
By methodically testing each function matching specs, teams confirm correct logic and workflows.
Visual Testing
Contrasting functional testing validating logic, visual testing analyzes aesthetic appearance. Visual tests capture and compare screenshots across browsers and devices to detect subtle rendering defects.
Front end visual tests check:
- Consistent UI styles, fonts, colors
- Accurate images, logos, and icon rendering
- Proper form and page layout
- Responsive design across viewports
Automated visual testing quickly identifies inconsistencies and deformation issues that frustrate users.
Accessibility Testing
Accessibility testing checks that sites and apps accommodate users with disabilities via standards like WCAG 2.1. Front end accessibility testing focuses on:
- Validating compatibility with screen readers for the blind
- Checking logical page navigation via keyboard for motor disabilities
- Ensuring adequate color contrast ratios for readable text
- Confirming appropriate alt text descriptions for images
Delivering accessible front end experiences expands your audience reach. Failing to test for accessibility risks exclusivity and legal penalties.
Cross Browser & Device Testing
With thousands of browser and device combinations accessing sites, compatibility testing across all platforms is mandatory before launch. Rather than assumptions during development, real user testing reveals front end defects on precise browser, device, and operating system combinations.
Cross browser testing provides hard data on real compatibility issues and performance across mobile devices. Identifying and fixing display and speed defects across browsers pre-launch dramatically improves user experiences.
Load & Performance Testing
While important for back end infrastructure, load tests also gauge front end stability under heavy user volumes. Performance testing meanwhile measures front end speed metrics like page load times, request latencies, and bandwidth consumption.
Optimizing front end load capacity and speed ensures smooth operations under peak demand without bottlenecks. Users will appreciate speedy performance thanks to pre-launch tuning.
Preferred Tools for Front End Testing
To maximize efficiency and effectiveness when testing front ends, using the right tools is imperative. Here are top solutions purpose-built to address typical front end testing challenges:
Selenium
Selenium allows engineers to write automated user interface tests across browsers and devices using a browser automation library. With a vibrant open-source community, Selenium supports languages like Java, JavaScript, C#, Python, and more.
Cypress
As a next generation front end testing framework built for moderns apps, Cypress enables reliable test automation for anything visible in the browser. Its readability, debuggability, and robust architecture accelerate test creation and upkeep.
Playwright
Created by Microsoft, Playwright provides unified APIs across Chromium, Firefox and WebKit to automate cross browser UI testing via a single test and framework. Superior to Selenium, Playwright delivers faster, more reliable test automation.
Applitools
Applitools utilizes sophisticated AI and machine learning for smart visual validation across browsers and viewports. Cloud processing identifies rendering defects instantly without test maintenance.
LambdaTest
LambdaTest constitutes an all-in-one cross browser cloud letting testers execute automated and live tests across 3000+ real desktop and mobile browsers online. Integrated dev tools assist test creation and debugging.
Challenges with Front End Testing
While delivering quality front ends is clearly pivotal, adequately testing complex interfaces poses formidable difficulties:
Exponential Test Matrices
Considering multiplying permutations of supported desktop browsers, mobile devices, browser versions, viewports and resolutions, exhaustive test coverage appears impossible. While 100% coverage via pure manual testing is unrealistic, test automation is indispensable for acceptable coverage. Choosing frameworks wisely drives test velocity.
Eliminating infrastructure overhead via cloud testing platforms also helps manage the testing scope.
App Complexity
Many modern web apps utilize diverse front end stacks including countless JS frameworks, libraries, emerging toolsets and moving parts that enable dynamic interfaces. Testing sophisticated components like single page apps with dynamic rendering, complex dependency injection, asynchronous cycles, WebSockets, Web workers and Service workers proves challenging.
Equally multifaceted test environments and frameworks are imperative to adequately cover components across integration points. Architecting tests early prevents uncaught defects later.
Frequent Framework Upgrades
Front end ecosystems evolve rapidly with new frameworks, updated browser versions, additional mobile devices releasing constantly. Each change introduces web compatibility defects and browser quirks that can break existing systems. Responding to every update with regression suites stresses teams to the extreme.
Access to Real Browsers & Devices
Testing across the diverse landscape of real desktop browsers, mobile iOS and Android devices is fundamental for an accurate pulse of real-world behavior. While simulators and emulators provide ballpark estimates, only real browsers and devices expose definitive user compatibility bugs.
Very few teams can justify the immense overhead and total cost of ownership associated with extensive in-house device labs. Relying solely on free cloud testing tools also poses challenges like limited testing minutes, lab availability constraints, difficult debug and integration capabilities.
CI/CD Integration Challenges
While continuous integration for automatic builds and continuous delivery for rapid deployment boost team velocity, incorporating testing into pipelines presents difficulties. Configuring test automation to maintain pace with CI builds while preventing quality gates from delaying deployments requires expertise and tailoring tools.
Analyzing Test Results
When executing expansive test suites across a multitude combinatorial test matrix spanning desktop browsers, mobile browsers, devices, and viewports, synthesizing high-level insight from the resulting mass of test data poses difficulties. Pinpointing patterns revealing chronic deficiencies demands tools with solid reporting abilities – areas needing attention get overlooked otherwise.
Best Practices for Front End Testing
Despite obstacles, applying proven practices positions teams to ship quality front ends quickly. Here are test automation optimizing tips from my decade of experience:
Architect With Testing in Mind
By architecting front ends intentionally for testability early on e.g configurable dependency injection and asynchronous handling, test creation overhead later reduces significantly. Designing loosely coupled modules also localizes changes needed when requirements evolve.
Start Testing Early
Introducing testing early shifts quality earlier catching defects before compounding across modules. High unit test coverage establishes confidence for integration and end-to-end workflow testing.
Implement Test Pyramids
Structure automated tests based on priority and scope. Numerous unit tests targeting discrete modules maintain quality; less critical integration tests validating component communication; followed by systemic workflow tests. Balance regression velocity with coverage.
Prototype Minimal Viable Product (MVP) First
Test a barebones MVP focusing on core functionality and priority user journeys first. Once basics operate across devices and browsers, build remaining capabilities on solid architecture.
Automate Testing
Automated tests executing repetitively scale coverage unattainable manually. Scheduled nightly automation prevents regressions so teams focus innovation not redundant checks. Parallel test execution enhances velocity.
Incorporate Visual Testing
Automated visual testing compares baselines and reveals front end changes instantly undetectable otherwise. Machine learning enhanced visual testing like Applitools ultrafast detects pixel-level anomalies.
Validate Accessibility
Automated accessibility testing followed by manual assistive technology testing ensures sites remain usable to disabled audiences and comply with standards.
Enable CI/CD Integration
By incorporating front end testing tools like LambdaTest into CI/CD pipelines, test automation scales release velocity, prevents regressions, and maintains quality standards – all while delivering rapid iterative updates. Careful test orchestration prevents pipeline delays.
Real Cross Browser Testing
While simulators have limitations in exposing real-world defects, services offering access to thousands of real desktop and mobile browsers online fuel comprehensive cross browser validation without infrastructure burdens.
Detailed Reporting & Analysis
Tools with intuitive dashboards, filtering, tagging, annotations, sharable reports, and visual data analysis accelerate root cause identification across massive test data sets spanning combinatorial test matrices.
Shift Testing Left
Transitioning testing as early in SDLCs as possible via unit level testing, maintaining test pyramids, and front loading automation establishes protection against accumulating downstream defects that erode user experiences.
Continuous Testing
By continuously executing automated test suites against pre-production environments throughout development cycles, defects surface quickly when introduced compared to dumping quality analysis until final user acceptance testing. Continuous validation reduces compounds issues.
The Path Forward
As web apps grow more complex, delivering exceptional cross browser user experiences mandates comprehensive front end testing capabilities firing on all cylinders.
By combining fundamental testing best practices with cloud testing environments and maturing test automation solutions, modern dev teams overcome obstacles and release higher quality front ends faster without infrastructure restraints.
With testing insights being synthesized via sophisticated analytics, issues that once overwhelmed now become actionable continuous improvements through consistent measurement.
