Testing helps find bugs to ensure that the software is working adequately.
Automation testing helps in saving time & effort from manual testing. A test orchestration platform evaluates your needs and tests accordingly.
Testers help find the errors and make the product efficient.
Testing is a continuous process & continues after release too. This helps in checking and maintaining the functionality of the product.
Finding all bugs during testing is impossible as there are bugs discovered on the go, and with new releases, bugs can be discovered.
It refers to that all the code has been executed at least once, but there might be test cases or scenarios that have not been considered.
As testing is a constant process, testing and development should go simultaneously.