I recall a problem reported by a customer years ago when I was working as a software tester on medical devices.
That bug on production was promptly and wisely managed by the Test Lead and the Software Area Manager: they assigned to me —the more recently hired employee within the team, by the way— an in-depth investigation of the functional area affected by that issue.
Should there be any other problems, we’d better discover them before our customers.
One of the first things I figured out was the fact that the regression testing periodically performed to verify that functional area was working properly had been limited, for years, to checking that all the fields and buttons which were supposed to appear on a specific page were actually there.
I quickly realized —in shock— that nobody had tested what happened when those buttons were clicked or when some of those fields were activated/deactivated.
So, I decided to do it myself.
To cut a long story short, as a result of my in-depth —and with fresh eyes— investigation, around twenty issues were found and some of them fixed, the other ones not being worth the risk.
Why am I explaining this now?
Because every time I receive a promotional message after having allegedly successfully unsubscribed from the corresponding newsletter, I feel nobody really tested what happens when clicking that button, nobody took care of data consistency, nobody verified that my email address was actually removed from that mailing list…
#ThisIsASeriousLackOfTestingMindset