Perhaps the most important step in writing software is performing quality assurance (QA) tests to ensure that it works the way that you want it to. To demonstrate how crucial this part of the programming process is, consider the recent controversy over the Healthcare.gov website, the launch of which was fraught with coding issues.
As soon as the site went live, users who were trying to access it in order to sign up for health insurance had a great deal of difficulty trying to complete their signups. Thousands of visitors were met with slow load times and other glitches, exactly the kinds of problems that the White House did not want to experience with the rollout of the Affordable Care Act (ACA). Given how much scrutiny was being placed on the launch of the site, it's safe to say that the Obama administration was hoping for a much smoother debut for Healthcare.gov.
Of course, now these problems are largely fixed, and people can access the site, but to this day, critics of the ACA point to the failed website launch as evidence of the administration's incompetence. Whether or not that's true is the subject for a different blog post, but it's easy to see how a similar situation could be disastrous for a private company that is introducing a new product to customers. Imagine the kind of reputation that firm would develop, and how difficult it would be to shed, if their website or software was filled with glitches and bugs.
This is why QA is such an integral part of the programming process. At Coder Foundry, we emphasize to our students that in order to be truly successful coders, they should master unit testing and other QA processes that will prevent disasters like the one that befell Healthcare.gov.