Development 101: How to Do Regression Testing

Continuous code changes are a fact of life in software development. However, each time your team adds a new feature, makes an update, or issues a patch, there’s justifiable nail-biting over the negative ripple effects it could create. Changing one part of code can lead to regressions (or “bugs”) that cause features or functions to stop working for users.

Your development team has probably heard of famous software update fails, such as the baggage handling system failure during the Heathrow Airport’s Terminal 5 opening or the Nest update that caused thermostat batteries to drain, leaving thousands of customers without heat. Although stories can be powerful motivators for developers, those who have experienced the fallout from a serious bug first-hand will not doubt that it’s critical to find them and fix them before they impact users. It’s obvious, but understanding how to do regression testing is critical to allowing a team to confirm that they’re shipping a clean update.

Regression Testing’s ROI

Although there is always pressure to get a release or update to market as soon as possible, an investment of time and resources into regression testing delivers a significant return. First of all, your team and your company’s leadership need to shift perspective from looking at regression testing as a cost center. Good regression testing actually decreases development costs overall. There is less cost associated with correcting regressions if you catch them early, rather than fixing them when the new version is live.

A study by the Systems Sciences Institute at IBM found that fixing bugs costs 6.5 times less if done before implementation, 15 times less if caught before beta testing, and 100 times less than the cost of maintenance once the update has been released. Costs associated with bug fixes are more than simply the direct costs of labor hours and rework. When a bug is discovered, your business will also experience losses in productivity and profitability when your development team’s focus shifts from coding to tracking down problems and remediating them.

Additionally, a regression can lead to lower user satisfaction and a negative perception of product quality, impacting revenue growth, customer retention, and, ultimately, a business’ valuation. The majority of users – 67 percent – cite bad experiences as their reason for churn, making it imperative for developers to perform regression testing, fix bugs that it uncovers, and push products that work the way users expect them to.

How to Do Regression Testing Right

The effectiveness of regression testing is heavily dependent on the process and standards you adopt. Solid testing procedures take these principles into account:


Again, it’s more cost-effective, efficient – and smarter – to move testing left, addressing it earlier in the development process. It’s also important, however, to decide exactly when testing will take place. Some teams tend to schedule testing at the end of an Agile sprint, but that timing may be too late for developers to track down bugs efficiently. If coding continues during the next sprint, team members will have to pause what they’re working on, take time to go back and pinpoint exactly which change caused the regression.

Continuous testing of every pull request, which gets feedback to developers more quickly, is usually the better approach. Why doesn’t everyone do this? Because their test suites are too large and the runtimes are too long to support continuous testing. Fierce prioritization of what tests you run (and don’t) is critical to being able to move your testing as far left as you can.


It’s not realistic to run a full suite of application-wide of tests every time developers make a change, so it’s vital to devise policies for prioritizing regression testing. The wisest strategy for setting priorities is to focus on software features and functions that users rely on the most. These are areas where bugs will be most detrimental to user experience (and ultimately, the software company’s brand and growth) versus a bug in an area that users rarely use or in a feature that is a “nice to have.”

Establishing priorities shouldn’t be left up to your quality assurance team’s intuition or best guesses. Analyzing user data will give you the ability to make intelligent decisions about testing priority.


Although you should focus on areas of priority, overall product quality is still vital. Ensure your regression testing process includes running your entire, application-wide testing suite at regular intervals to find bugs so that your team can address them. Finding lower-priority bugs later in the software development lifecycle is still a win.


Even though regression testing early in the process saves time overall, and running the full suite of tests is integral to quality assurance, it still takes time to execute. And that’s probably time development teams will have trouble finding in their busy schedules. A well-developed automation strategy solves that problem, enabling teams to run high-priority tests at high frequency, and application-wide tests as needed, without adding to developers’ workloads.

Don’t Choose Between Code Quality & Deadlines

Well-prioritized regression testing, based on data-driven priorities and managed with automation, provides development teams with greater efficiency and the ability to deliver quality applications as well as speed to market.

It’s a formula for a successful operation in which developers spend the lion’s share of their time writing code, not searching for bugs and correcting them – resulting in a more productive, positive company culture. An optimized regression testing strategy will also help to deliver applications with the features, functionality and UX users expect and build customer retention and a growing business.

Don’t choose between quality and timeliness. With the right regression testing strategy and the right testing tools, your business can have both.