You're right, of course, in that there are many things that work much of the time and then fall apart under some application-specific timing or sequence. Rigorous testing exposes those, while superficial "try it and ship it" often doesn't. That's why the test has to be designed before the circuitry. That way you design the circuit to meet the required test criteria rather than trying to invent criteria that your circuit will survive once the boards are assembled.
If you read my posts on this subject, you will see that "testing" will not be found without the quotes. Were I to discuss it on the premises above, the quotes would disappear.

what you correctly refer to as "try it and ship it" is called "testing" by most.

You state above "design the circuit to meet the required test criteria" which I would state "design the circuit to meet the required criteria flawlessly". No criticism of your statement, I just prefer the other.

Erik