Properly written automated regression tests are deterministic. A computer will doggedly follow exactly the same test algorithm every time. There is no human variability. Test determinism is the necessary prerequisite for regression testing. A software company that doesn't have deterministic automated tests, can't say they're doing regression testing with a straight face. We run regression tests for each release, so they save us money every time they're run.
Everything about information systems scales geometrically. Hiring thousands of manual testers isn't an option. Some of the most important system, soak, load, and performance tests are literally impossible without automation. Automating these tests literally makes some software products possible and translates into higher product quality and more business.
Run Tests Early and Often
It's not necessary to wait until code freeze to begin to test. Automated tests allow testing to begin immediately after a new release is branched. Some people call this continuous testing. This helps assure quality stays high throughout development and therefore higher quality when QA starts qualification testing. Automated tests can be run nightly, or even with every build. And every time they're run, they pay us back.
Automated tests allow developers to get immediate feedback when they break the product. They can run automated tests prior to check-in to pre-empt the costly triaging necessary in post-checkin integration testing. Bugs that can be found prior to check-in, should be. QA is a circuitous and therefore expensive way to find bugs. We save money every time a developer finds his own bug.
Testing early and often reduces the bug backlog entering QA qualification. Fewer bugs entering QA qualification means more reliable delivery. Reliable delivery means cheaper production, wider margins, and more business.
System, soak, and performance tests and utilities can be written to scale. Executing an automated test with 1,000 client systems can be done with same command that launches the test for 1 client. People are the biggest expense in testing. Scalable tests allow a limited staff to command ever-growing testbeds, saving personnel expense.
The nirvana of automation is automatically executing automated tests. Automated tests can be run as a batch from a scheduler like cron or in an event driven way upon each check-in, further reducing human costs and allowing personnel to focus on writing new automated tests and triaging test results. We save money when QA can focus on better testing.