Shooting with hail or just one test case?

Almost every one wants to setup a controlled test process.

It is if we are playing the song "Proud Mary" by Ike & Tina Turner: "Take the beginning of this song and do it easy. Then we're gonna do the finish rough."

We always start simple with a controlled set of test cases. Often these test cases are based on the outcome of using test techniques. So far so good.

Still we might become lazy over time. If errors are found in production, we re-test the solutions and add the test case to the test set. There is less time to question the system and our test process what went wrong and what can go better.

In manual testing after some short time you will see that keep adding those test cases to the test set will make our process "rough" as we don't have time to execute all test cases or select a common sense set of cases. Business is already relying on us and demanding that all is done.

In automated testing this time pressure is almost minimized. We can keep adding new cases, let the number exceed over the thousands and still continue and deliver.

This reminds me about the phrase: "A bird in the hand is worth two in the bush"
If we accept the meaning of this phrase we are we not able to continue controlling that bird in our hand and instead sewing our own bush?
It is easier to take care of a bird we know then nurse the birds in the bush. If we feel we need another bird, just let the bird free and pick another out of the bush. Not just the first one which fell in your arms, go into the bush and see which sounds the best to your needs.

Keep it simple and easy, enjoy the roughness and prevent to get stucked on numbers. Don't create a process where you are shooting with hail on the system.