Software is the most complex thing humans create. Most programmers can't write 10 lines of code without any errors occurring. Now, take this common knowledge and consider what it takes to write a distributed system made of tens, hundreds, or thousands of interacting components that have been designed and implemented by large teams using lots of third-party dependencies, lots of data-driven logic, and lots of configuration. Over time, many of the original architects and engineers that built the system might have left the organization or moved to a different role. Requirements change, new technologies are reintroduced, and better practices are discovered. The system must evolve to meet all of these changes.
The bottom line is that you have zero chance of building a working non-trivial system without rigorous testing. Proper tests are the skeleton that...
