Snapshot v/s Visual tests whose responsibility is it anyway?

A fantastic user experience can set apart a product from the competition already present in the market. Visually appealing software is urgently needed. Testing the user interface is not only necessary but also a must with the growing use of mobile devices, tablets, and laptops. Many businesses employ A/B testing and other strategies to monitor end users’ behavior and continually improve their user interfaces in an effort to give them the best possible experience.

Front-end testing sometimes referred to as client-side testing, is the process of evaluating a website or online application’s user interface and user experience from the end user’s point of view. Front-end testing includes verifying that the user interface is aesthetically pleasing, simple to use, and operates as intended across a variety of platforms and browsers.

For instance: In the luxury eCommerce sector, brands are required to offer the same experience to customers as they proudly enter the store and make major brand purchases.

Because so many different people use banking software, the user experience in the retail banking sector cannot be modified regularly. Additionally, those who are not technologically advanced may find it confusing.

It is impossible to overstate the value of front-end testing. Teams can use 2 primary automated tests to obtain consistent test execution for frontend development.

a) Snapshot tests

b) Visual regression

Let us look at each test in detail

Snapshot test

Snapshot tests are designed to confirm the structural characteristics of individual components and component sets, directly assisting with micro-level visual testing. These tests use test renderers to display the components’ actual DOM structures, then compare the output to an expected structure that is stored alongside the test in a reference snapshot.

You must have heard about Jest, react-test-renderer etc.

During the development stage, these tests enable quick input on the structural properties of components. When components are utilized in various applications, as in design systems, these checks become crucial. They are created as part of the development process and remain inside the development code base, just like unit and integration tests.

Snapshot tests are advised to keep a tight focus, such as evaluating a single small component or a quite larger component that won’t frequently change. For the goal of preventing regression, it is advisable to write them after the components are created. Otherwise, whenever there is even a little change in the layout, more work will be needed to maintain them.

** Who should add snapshot tests?

Snapshot tests should be added by front-end developers who create UI components, and these tests should be run frequently as part of the development workflow.

** Should the Test engineer participate in adding snapshot tests?

A test engineer can contribute by adding any tests to improve the application, but front-end engineers are mostly responsible for these tests.

** Does the snapshot test verify the application’s behavior?

Snapshot tests won’t perform any business validation; instead, their intent/goal is to ensure that components are rendered on the UI as intended.

**What are the downsides of snapshot testing?

When DOM updates occur, snapshot testing still requires manual intervention, and it is often seen that front-end developers update the base snapshot without first determining what caused the test to fail.

Visual Tests

Although the technique for visual testing is similar to that of snapshot tests, the test objective and general execution pattern are different. The concept of an E2E test includes visual testing, often known as visual regression tests. Visual tests focus on multiple component at a glance and verify these components are in sync.

Open source tools like Cypress, Galen, BackstopJS, and others can be used for this purpose.

To comprehend the new UI components being developed and their placement on the frontend, test engineers must work more closely with front end developers. Before arriving at the target screen for comparison, visual testing could additionally require that some business operations be completed.

** Who should add Visual tests?

Its test engineers responsibility to include visual tests in their test automation routines.

** Should the Frontend developer participate in adding visual tests?

A frontend developer can contribute by adding any tests to improve the application, but test engineers are mostly responsible for these tests.

** Does the Visual test verify the application behavior?

Ideally not, Visual tests goal is simply to verify the UI behavior and not to validate business functions. However, to achieve a desired UI state test engineer may have to perform the required business action before taking the snapshot.

** What are the downsides of Visual testing?

On applications with animations, high-density graphics, movies, automatic image loading, etc., visual tests cannot produce consistent results.

Further reading:

Mastering React Test-Driven Development – Daniel Irvine, Justin searls

A Frontend Web Developer’s Guide to Testing – Eran kinsbruner, Gleb bahmutov

E2E testing with Cypress


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