The necessity of tests
Tests are necessary to be able to rely on that a certain functionality behaves in a certain way later in production. In all kinds of manufacturing businesses, tests are a natural part of the process. A car has countless parts that need to be tested independently as well as interdependently. Nobody wants to drive a car which has its first test run on a real street with the actual customer.
Tests simulate production behavior and verify components in a safe environment. Manufactured parts that break during test runs are something positive; they have just pointed out potential errors and nothing more than time and materials is lost. Parts that break in production can cause more harm.
The same is true for software tests. Test failures are something positive, at worst they used up some time and effort, at best they prevent potential bugs from going to production.
As seen previously, tests need to run with the least required human interaction possible. Humans are good at thinking...
