Input validation issues are linked to website forms. Whether it's an entire page asking for personal information or just one field to enter an email address to sign up for a newsletter, this validation is essential because it verifies at least one of the following scenarios: the user entered information within a mandatory field, entered the correct type of information and followed the expected format.

If the scenario needed is not met, the system will tell users that the input is invalid, commonly by displaying errors like a message next to the corresponding input field, showing a summary of all errors at the top of the form, or using pop-up notifications.

Sometimes the error is provided as visual feedback, visual cues to highlight the fields with incorrect input. This can include changing the field's background colour, adding an icon or border, or applying other visual indicators to draw attention to the problematic input.

Solid comprehension of how forms are validated is crucial for conducting comprehensive testing.

Depending on the design, some users' information may be more critical than others; this is why sometimes forms accept letters in a telephone number field or numbers in a surname field, and this is also why websites validate users' inputs differently.

Let's look at how a validation might be implemented to guide your testing to avoid common mistakes while testing.

If the validation system occurs only after submitting the input to the server, this type of implementation is called server-side validation, in which a web server is the one that performs the validation after, usually, the user has clicked on a button like ❝Submit❞ or ❝Send❞.

However, the most commonly implemented validation is when you, as an end-user, expect that a validation triggers upon entering an incorrect input. This type of expected validation is performed locally by the browser and is called client-side validation, in which the ideal case is seeing a read message displayed next to the field to tell users what went wrong.

However, when the expected red messages do not appear upon entering incorrect input, the most likely reason for that is not a bug but a different validation system that has been implemented.

One of this validation system's most common ways is in the email address field.

On the other hand, a third option that might be implemented is hybrid validation (Dual Validation) which combines server-side and client-side validation for a more comprehensive validation process. It leverages the benefits of both approaches.

Client-side validation helps provide instant feedback to the user and improves the user experience, while server-side validation ensures the data integrity and security of the system. With hybrid validation, the form data is validated both on the client and server sides, providing an extra layer of validation and increasing the overall reliability of the form.

So, whenever you test a form, consider these three ways to validate users' input before submitting a bug report to prevent rejections and efficiently power up your testing process.