Front-End Testing Strategy: A Detailed Guide

Front-end refers to the client-facing part of an application, which acts as the primary interface for content consumption and business transactions. Although the term was coined for web technologies, it is also applied to and used for mobile applications, as they have similar segmentation in structure.

Different development platforms follow different testing strategies and implementation methodologies. This guide will walk you through the common principles on which a sound front-end test strategy can be built.

Front-End Testing Fundamentals

Which team members work on front-end testing?

In a modern application infrastructure stack, there are crucial layers:

• Server-side, also known as the back-end, includes data access, business logic, and administrative layers of the program. It lives in a secure computing environment and has access to databases and other integrated technologies involved in computation and transactions.
• Client-side: also known as the front-end, this is the code bundle that loads on the device the user is accessing the application. The client-side bundle has its own set of packaged dependencies and functionalities. It communicates with the server-side/back-end and is a secure interface between the user and data.

Testing the client side of the app is known as front-end testing. The parameters of a front-end test strategy are guided by the user’s needs and the device platform constraints.

The front-end/client could be one of the many available device platforms, depending on the use case. In the case of a mobile app, it is the mobile device OS. In the case of a web application, it is a web browser running on top of an OS.

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When thinking of testing front-end, various types of tests can be implemented in the form of layered plans, we can broadly break them into the following categories:

• Unit Testing: this is the first testing layer built into the codebase itself. It includes test functions that run before the application is built and tests various individual functions and modules.
• Functional Testing: running the app and testing features and components through a manual user interface on the front end. At this stage, all the content is usually mock data.
• Integration Testing: wiring up the front-end components to back-end services and ensuring proper integration from client inputs, through APIs, to database management, running at this stage on a test environment.
• System/UI Testing: after a test version of the user interface has successfully been integrated with the test back-end service, the application is now ready for automated testing and analysis by developers working closely with the QA team.
• Performance/Load Testing: Performance testing verifies that an application can handle the expected load and scale. The application response and behavior quality focus, considering the optimal load and usage scenario.
• Stress/Security Testing: Stress testing verifies that an app can handle unexpected load and scale. It also evaluates the response when it is hit with usage and threats beyond the expected limit.
• Accessibility Testing: Accessibility testing verifies that people with disabilities can use an application. 

These tests could be sequential or parallel as per need. To build complicated test flows ensuring strict adherence to quality standards across platforms, browsers, and devices, we need to understand what to test and how to test.

How to perform Front-End Testing?

Testing modern applications is not an activity that is performed at the end of development. Instead, it is a deeply ingrained part of the development process itself, so for us to understand what to test during front-end testing, we need to understand the stepwise sequential nature of each test:

• You can use plain JavaScript or popular frameworks like Angular, React, Vue etc., to build web applications or PWAs. Using proprietary development setups, you can build native mobile apps for Android or iOS.
• Writing unit tests with individual application components is the first place to start with front-end testing. All major frameworks support built-in modules and syntax for executing unit tests.
• Once you complete one module/feature set of the application, you can run it and test the visual output with the help of mock data; this is called local testing. 

Developers at this point are using web browsers or mobile device emulators/simulators bundled within the IDE or third-party apps for testing the visual output on the development machine. 

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• After manually validating a single module, it is time to plug it into the server side and test the integration with the test server. At this stage, the data is also being mocked but on the server side, not the client side.
• The communication between the client and server-side occurs through requests working on contracts, also known as APIs, which have to be tested separately.
• Once you have a module functioning correctly with the server-side integration, developers can focus on the look and feel aspects by referring to the specifications mentioned in the design documentation and implementing them accordingly. 

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• Once a module is ready with test server integration and design specifications implemented, it can be passed on for automated visual regression workflow set-up. 

The goal is to develop automated processes, run on the cloud and routinely execute meaningful business test cases for analysis.

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• After completing the abovementioned steps, developers usually commit code for approval into the master repository. 

In a Continuous Integration (CI) setup, this step will be a trigger for running a build on the cloud, which creates a test version of the application on a test environment to be tested by QA independent of the developers.

In modern systems based on cloud, microservices, and modularization, teams are broken down into sub-teams following agile with CI/CD as the standard industry practice.

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Front-End Testing Strategy as per Business case & Team structure

Front-End Test Frequency and Cycles

Since there are multiple steps and more than one type of testing involved in the process, the frequency, duration, and periodicity of test execution depend on the present stage of the product in its evolution cycle.

Take an example of testing on three environments for simplicity i.e. 

1. Developer’s local environment 
2. A test environment 
3. Pre/Production environment. 

Whatever test plan is devised will be executed upon each build on each environment, creating multiple reports for each test type, stage, environment, etc.  Assuming every test is successful, which if not mean additional debugging work.

Once you have automated a significant portion of the testing process, you can increase the release frequency to a degree.

The build release frequency will still depend on other variables like:

• How often does the business require you to release updates?
• What are the resource and cost constraints for releasing a new build?
• Are there any security considerations while releasing new builds?

What do you focus on during testing?

Since web applications don’t require installation on the client side, they can be updated much more frequently than mobile or desktop applications. 

Mobile applications need software bundles to be explicitly downloaded and installed or updated before any new changes can be incorporated. 

Here are general guidelines for different release frequencies:

• A robust automation testing workflow is a must-have for teams aspiring to release daily or multiple times a week.
• Both web and mobile app developers can use weekly builds as they provide enough time to run rigorous automated testing and are fast enough in scenarios where updates are required.
• Unfortunately, mobile and desktop apps will require frequent downloads on the user’s side, which is not a great experience.
• Monthly builds provide much more time for validating the application but are unsuitable for fast-evolving products.
• Products growing steadily and approaching maturity can significantly improve on such a schedule.
• Yearly builds are the favorite release cycles in the current industry for device manufacturers, operating system providers etc. They require more time than mobile or web apps to evolve and change.

Performance, Security, and Optimization

Performance and security are not less important. Still, when an application is being designed from the ground up, the considerations for performance and security are relaxed until the application’s core functionality and experience are not adequately defined.

Once a stable version of the application is built, tested, and deployed for users, this is where serious effort goes into a performance, security testing, and optimizing the broader infrastructure.

Wrapping Up,

• Once users have access and start using the app, various performance metrics for the system infrastructure and application internals can be recorded and analyzed. Similarly, testing on the live version will give the most realistic outcomes for security.
• Because of the infinite flexibility of digital systems, teams can have different development and product release cycle workflows. Anyone can have a daily/nightly build for the internal test version, which is separated from the production environments.

The best front-end testing strategy for your application is a call you will have to make after studying and carefully considering the constraints for the team, resources, and business. We hope this guide will help you make the right choices for your testing effort.