What to rely on when testing if there is no specification?

Question

Software testing

Hello.
I took up testing. There is such a question. If you need to fully test the search form on the mobile version of the site, but there is no specification, what is the right thing to do? Rely on common sense and sort out many possible options, while compiling cases in parallel? Or is there some standard for testing forms?
Thank you.

Answer 1

1. Common sense - yes. Check that the application is behaving
2. We constantly keep in mind why this form was created at all - we get an approximate list of expectations.
For example, this is a feedback form - it is clear that the email field should check for correct input. It is clear that the Phone field must accept numbers. It is clear that the Feedback field must be more than one line (textArea), and so on.
3. Asking questions to the Manager/Analyst/Customer (someone who understands better than us why this form is needed)
And black box testing does not imply the absence of requirements. You, as a tester, can be given a ready-made mobile application. It will be a black box; you don't know how it works inside, what servers it accesses, etc. But you may well have requirements for this application

Answer 2

In addition to the excellent post above:

1. Use the user manual
   Here you will find tests in a primitive format, and understand the approximate requirements.
   
2. Focus on the system itself
   Examine the places where the system can contradict itself. Remember that the operation of each element of the system is usually similar to its neighbors.
   

Answer 3

You should check the competence of your mentor. The statement "fully test" contradicts the fundamental principle of testing "Exhaustive testing is impossible".
I propose to ensure a sufficient level of quality. We will approach the definition of this from the managerial side.
No specification? It needs to be done. I suggest the following way: imagine what is most important from a business point of view in this form (examples: search for an existing object, protection against SQL injection, search by additional settings, error handling such as searching for a non-existent object) and put it in the list. IMPORTANT: include in the list only those items without which the form cannot be considered working or meeting the requirements of the business. The list is entitled "Acceptance criteria" and carried to the customer for signature. Without this signature, he has every right to soar your brain with questions like: why didn’t you test this (or that)? And with a signature, you will have a document that determines sufficient quality at the user acceptance level.
Passed the tests? This means that the acceptance criteria are met. Want more tests? We are agreeing on a new specification, an additional budget for testing and expanding testing to a new level (I hope your mentor told you about testing levels?).