It's impossible to deliver a great user experience if your application lacks a reliable, user-friendly front end – which is why front-end testing is such a critical part of any software testing strategy. Indeed, although it would be wrong to say that front-end testing is more important than other types of testing (like back-end tests), it would be equally wrong to under-invest in front-end tests.
Keep reading for a dive into what front-end testing means, how it works, and why it's so important.
What is Front-End Testing?
Front-end testing is testing that validates the user-facing components of an application. Front-end tests can evaluate features and functionality like the following:
How an application renders images and whether they appear on a screen as intended.
How easy it is for users to find and access application features, such as buttons.
Whether application elements respond quickly enough to user interactions.
How different configurations (such as different device types or browsers) impact the appearance and functionality of an application's front end.
A focus on these elements makes front-end testing distinct from other types of testing, such as back-end tests (which focus on data processing routines and management that take place behind the scenes and are hidden from users) and security tests (which check applications for vulnerabilities). Testing all of these elements creates a comprehensive end-to-end testing strategy that improves the overall functionality of an application.
Front-End vs. Back-End Testing
To provide more context on how front-end testing is different from back-end testing, let's compare these two types of testing.
The main differentiators include:
The parts of the application that are tested: Front-end tests validate application components that are visible to users, whereas back-end tests focus on application logic and data processing components that exist "under the hood."
Testing tools: Engineers may need different tools for front-end versus back-end testing because application front ends can be written in different languages than back ends, and some testing tools support only certain languages.
Types of tests: Certain types of tests don't apply to back-end testing. For example, you wouldn't perform user experience testing for the back end because the user doesn't directly "experience" the application back end. Instead, you'd rely on techniques like performance and load testing to ensure that the back end contributes adequately to the user experience you require.
Table: Front-End vs. Back-End Testing
| Focus | Tools | Testing types |
Front-End Testing | Application components that are directly visible to the user | Tools that support front-end programming languages and elements | Any type of test that directly evaluates how a user experiences the application front end |
Back-End Testing | Back-end components, like databases and data processing routines | Tools that can test application performance on the back end | Tests that measure the performance and reliability of the application back end |
Why is Front-End Testing Important?
The reason why front-end testing is important is simple: an application's front end is at the center of the user experience, and problems with the front end will dramatically impair user satisfaction.
After all, even if your application is excellent in all other regards, problems with the front end may render the application unusable. The application could be highly responsive to requests, but if the buttons that users need to access application functionality don't appear where they are supposed to on the screen, the app's ability to handle requests is meaningless. Likewise, you could have the most secure application in the world, but if users struggle to navigate its interface, the application won't deliver any value.
Benefits of Front-End Testing
Front-end testing delivers several key benefits that help shape a positive overall user experience:
Bug detection: Front-end tests can help with debugging issues such as problems in stylesheets that cause visual content not to display in the proper location.
Improved user interface: By identifying interface elements that users dislike or find confusing, front-end tests help developers improve visual interfaces.
Faster development cycles: Front-end tests help root out visual bugs and hone in on visual features that users find most appealing. In turn, developers can work more efficiently, which leads to faster development cycles.
Consistency: By evaluating the appearance and performance of front-end components across different types of devices and software environments, front-end tests help ensure that applications work consistently no matter which environment users are operating in.
Challenges of Front-End Testing
On the other hand, front-end testing can present some challenges:
Inability to automate all tests: Although many front-end tests (such as those that evaluate whether a visual element appears where it's supposed to on a screen) can be automated, some (like tests where users provide feedback about how confusing they find an interface) must be performed manually.
Complexity: Application front ends are often complex. A navigation menu could include many sub-menus and nested items. Plus, some visual elements may only appear if users hover over them or click on them. Factors like these make front-end testing complex and require engineers to think strategically about exactly what to test and how to test it.
Subjective test results: Some feedback from front-end tests, such as opinions about how user-friendly an interface is, is subjective. For this reason, it's important to interpret front-end testing results with some nuance. Some users may hate certain front-end components while others love them, in which case it's necessary to decide which opinions to prioritize – or modify the front end in a way that caters to both groups by, for example, allowing users to customize an application's interface according to their preferences.
Types of Front-End Testing
There are many types of front-end tests available to developers and QA engineers:
Visual/UI tests: Automated visual tests that determine whether interfaces and visual elements render as intended within an application are a basic component of most front-end testing strategies.
Performance tests: Performance tests evaluate how responsive an application is and whether user actions result in errors. In the context of front-end testing, performance tests can provide insights like whether users see results quickly enough after clicking a button, as well as how long it takes different parts of an interface to load.
Accessibility testing: By validating that an application interface works adequately for users who rely on accessibility software or features, accessibility testing helps ensure that an application front end meets the needs of as many users as possible.
User experience testing: User experience testing relies primarily on manual tests to solicit feedback from human users about how well they like different aspects of an application's front end, such as its navigation menus and content layout.
Unit tests and integration tests: It may be a stretch to call unit testing and integration testing, which are used to test source code early in the software development process, a type of front-end test. But if the code units that you test relate to front-end features or functionality, they could fall within this category.
Each type of front-end test evaluates a different aspect of the application front end. Thus, depending on exactly what you want to test, you may choose to run certain front-end tests versus others.
Front-End Testing Tools
Developers and QA teams can perform front-end testing using a wide range of testing frameworks. Popular options include:
Selenium, an open source test automation tool that works across all mainstream browsers and operating systems.
Puppeteer, a tool designed for headless test automation of Web apps via Chrome and Chromium.
Cypress, a test automation tool for JavaScript.
Jest, another testing framework designed primarily for JavaScript apps.
Of these options, Selenium is probably the most versatile front-end testing tool because it can work with different types of apps, not just those that are based on JavaScript. But since the front ends of most modern apps rely heavily on JavaScript, the other tools (which are all JavaScript-centric) will serve most front-end testing needs, too.
Front-End Testing: A Step-By-Step Guide
The exact approach that a team takes to front-end testing will vary depending on factors like which types of front-end tests they want to perform and which testing tools they use. But in general, the front-end testing process boils down to these steps:
Decide what to test: Identify the specific front-end components you want to test.
Choose manual vs. automated testing: If the components can be tested manually or automatically, decide which method to leverage. Automated testing is faster and more scalable, but it requires you to write tests, which may be more effort than it's worth depending on how many times you plan to use the tests.
For automated tests, choose a testing framework: The test automation framework should be able to support whichever types of automated tests you want to run.
Choose a testing infrastructure: Decide where to run your tests, such as on a device cloud.
Run the front-end tests: Execute the tests using the manual or automated methods you selected earlier.
Interpret test results: Evaluate the test data to identify any bugs or other issues. Remember that, as noted above, manual front-end test results may be subjective, so you'll need to assess whether problems reported by users reflect real issues or just preferences.
4 Best Practices for Front-End Testing
The following practices can help teams get the most out of front-end tests:
Run other tests first: Before performing front-end testing, run more basic types of tests, such as unit and functional tests. These tests often catch basic bugs that may impact your front end, allowing you to root out simple problems before you get into more complex front-end testing routines.
Prioritize the most popular front-end elements: An application front end may contain many different features and components, and you may not be able to test each one. To ensure that your tests deliver the greatest possible value, focus on testing components that are most widely used or (if you don't have data about actual user behaviors) are likely to be most popular among your users.
Select representative users for testing: If you perform manual front-end tests, do so with users who are representative of your actual user base. For example, if most of your users lack deep technical expertise, having your own developers perform the front-end tests is not very useful because your developers are more likely to be "power users" than the majority of your user base.
Use unbiased testers: Another reason why you typically shouldn't perform manual front-end testing with members of your own team is that they are implicitly biased because they know how the application front end is "supposed" to work (because they were involved in building it). It's better to test with objective outsiders who have no preconceived notions or knowledge of the app.
Repeat and scale tests: The more often you perform tests, the better able you will be to detect issues that may arise only under particular environments or configurations. This means you shouldn't run front-end tests on just a handful of device types, or just for one application build. Run your tests comprehensively and repeatedly across many devices.
Conclusion: Getting the Most From Front-End Tests
Identifying which front-end tests to perform, then running them efficiently and continuously is a critical part of any software testing strategy.
Sauce Labs makes front-end testing easy. With a testing cloud that allows teams to test apps across virtually any device, browser, and configuration using a wide variety of testing frameworks and tools, Sauce makes scalable, continuous front-end testing a breeze.
