When everything runs on software, from your uncle’s bakery to the country’s economy, the demand for new capabilities grows exponentially, and the more critical it becomes to ship software that works and ship it frequently—hopefully, multiple times a day. That’s what automated tests are here for. Long gone is the time when programmers could afford themselves the luxury of manually testing their software every once in a while. At this point, writing tests is not only good practice, it’s an industry standard. If you search job postings at this very moment, almost all of them require some degree of knowledge about automated software testing.
It doesn’t matter how many customers you have or the volume of data you deal with. Writing effective tests is a valuable practice for companies of every size from venture-capital-backed Silicon Valley giants to your own recently bootstrapped startup. Tests are advisable for projects of all sizes because they facilitate communication among developers and help you avoid defects. Because of these reasons, the importance of having tests grows proportionally to the number of developers involved in a project and to the cost of failure associated with it.