Slow Tests Kill Businesses

I’m always surprised at how few organisations track some pretty fundamental stats about software development, because if they did then they might notice what’s been killing their business.

It’s a picture I’ve seen many, many times; a software product or system is created, and it goes live. But it has bugs. Many bugs. So, a bigger chunk of the available development time is used up fixing bugs for the second release. Which has even more bugs. Many, many bugs. So an even bigger chunk of the time is used to fix bugs for the third release.

It looks a little like this:

Over the lifetime of the software, the proportion of development time devoted to bug fixing increases until that’s pretty much all the developers are doing. There’s precious little time left for new features.

Naturally, if you can only spare 10% of available dev time for new features, you’re going to need 10 times as many developers. Right? This trend is almost always accompanied by rapid growth of the team.

So the 90% of dev time you’re spending on bug fixing is actually 90% of the time of a team that’s 10x as large – 900% of the cost of your first release, just fixing bugs.

So every new feature ends up in real terms costing 10x in the eighth release what it would have in the first. For most businesses, this rules out change – unless they’re super, super successful (i.e., lucky). It’s just too damned expensive.

And when you can’t change your software and your systems, you can’t change the way you do business at scale. Your business model gets baked in – petrified, if you like. And all you can do is throw an ever-dwindling pot of money at development just to stand still, while you watch your competitors glide past you with innovations you’ll never be able to offer your customers.

What happens to a business like that? Well, they’re no longer in business. Customers defected in greater and greater numbers to competitor products, frustrated by the flakiness of the product and tired of being fobbed off with promises about upgrades and hotly requested features and fixes that never arrived.

Now, this effect is entirely predictable. We’ve known about it for many decades, and we’ve known the causal mechanism, too.

Source: IBM System Science Institute

The longer a bug goes undetected, exponentially the more it costs to fix. In terms of process, the sooner we test new or changed code, the cheaper the fix is. This effect is so marked that teams actually find that if they speed up testing feedback loops – testing earlier and more often – they deliver working software faster.

This is very simply because they save more time downstream on bug fixes than they invest in earlier and more frequent testing.

The data used in the first two graphs was taken from a team that took more than 24 hours to build and test their code.

Here’s the same stats from a team who could build and test their code in less than 2 minutes (I’ve converted from releases to quarters to roughly match the 12-24 week release cycles of the first team – this second team was actually releasing every week):

This team has nearly doubled in size over the two years, which might sound bad – but it’s more of a rosy picture than the first team, whose costs spiraled to more than 1000% of their first release, most of which was being spent fixing bugs and effectively going round and round in circles chasing their own tails while their customers defected in droves.

I’ve seen this effect repeated in business after business – of all shapes and sizes: software companies, banks, retail chains, law firms, broadcasters, you name it. I’ve watched $billion businesses – some more than a century old – brought down by their inability to change their software and their business-critical systems.

And every time I got down to the root cause, there they were – slow tests.

Every. Single. Time.

Author: codemanship

Founder of Codemanship Ltd and code craft coach and trainer

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