A bug doesn't always need bad code to reach production.

In fact, some bugs silently pass through a process where everyone is doing the right thing.

A developer writes the code.
The code is reviewed.
The tests are run.
The pipeline is green.
Everything seems fine.

Then the user comes along and disrupts the system. :)

So, how does the bug get here?

Because successful tests don't mean that a system is error-free.

A test only checks the scenario it was designed to test. If a bug exists in an unexpected scenario, the test naturally can't catch it.

For example, let's consider a payment system.

Our test might check something like this:

The user makes the payment → the payment is successful → the order is created.

Everything passes.

But what happens if a real user presses the payment button twice?

This is where a bug can survive.

That's why a good test engineer doesn't just ask:

"Does this work?"

There is a more important question:

"How can I break this?"

Because a good test focuses less on proving that the system is working correctly and more on finding where it might go wrong.

Maybe a bug's greatest talent isn't making a mistake; it's hiding where no one is looking for it.