Why Do They Test Software?

My friend Rachel Kibler asked me the other day "do you have a blog post about why we test software?" and I was surprised to find that, despite having touched on the topic many times, I haven't.

So then I thought I'd write one.

And then I thought it might be fun to crowdsource so I asked in the Association for Software Testing member's Slack, on LinkedIn, and on Twitter for reasons, one sentence each.

And it was fun! 

Here are the varied answers, a couple lightly edited, with thanks to everyone who contributed.

Edit: I did a bit of analysis of the responses in Reasons to be Cheerful, Part 2.

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Software is complicated, and the people that use it are even worse. — Andy Hird

Because there is what software does, what people say it does, and what other people want it to do, and those are often not the same. — Andy Hird

Because someone asked/told us to — Lee Hawkins

To learn, and identify risks — Louise Perold

sometimes: reducing the risk of harming people — Ilari Henrik Aegerter

since part of software is a complex system: To reveal unknown unknowns — Ilari Henrik Aegerter

but unfortunately also: as a masochistic self-medication practice — Ilari Henrik Aegerter

my definition: “Testing is the art of finding out what software can do, where it fails to do what it claims, and what else the product does that might be surprising” — Ilari Henrik Aegerter

We test software because between what business wants and what engineers deliver, a lot of information gets lost/filtered/unexplored. And it is important to find that information and bring it on the table for everybody to know what to do next —  Lalit Bhamare

I took this one from a list of Software Testing Myths: "Testing is a measure of quality. The number of defects you find indicates the quality of the product." — Dusty Juhl

Testing is important because of risks we know about and risks we uncover during the activity. — Rachel Kibler

Testing is funtastic. — Aleksandar Simic

Living for testing, testing for living. — Aleksandar Simic

It depends on what I'm testing at the moment.  Lately I test to ensure we are releasing the product/feature that our company wanted to release, and that users will enjoy. — Joel Montvelisky

For me testing has always been a service,  as such the most important thing is to fulfill the needs we were brought to provide.  — Joel Montvelisky

If I needed to come up with a general umbrella reason for my testing… it would need to be around reducing the risk of disappointing / harming the people who will eventually work with our product  — Joel Montvelisky

It costs less than not testing. (in terms of reputation, hotfixes, etc) — Amit Wertheimer

It provides some ease-of-mind to the decision takers, and sleeping well is valuable. — Amit Wertheimer

In both cases, it's not always true, and if so - we should not test. If there's a way to gain enough confidence to sleep well, or have a way to avoid problems without testing, we should definitely explore it. — Amit Wertheimer

I work in testing because, in college, while I did well in my programing classes I wasn't the top of my class, whereas I was the top of my software testing classes. Since, virtually no-one else even had testing classes I could be a rock star there. — Curtis Pettit

I stay in testing because, its more fun, I'm still better at it, and I can avoid most of the non-programming problems that devs have, fighting with builds, monitoring tools, ect. While still writing as much code as I like. — Curtis Pettit

Because we prefer most of the feedback on our software to be deliberate feedback. Deliberate as in: influence and/or control over the what/when/how/... allows it to be more timely, more information-rich, more actionable. — Joep Schuurkes

We test software, to help make design decisions. — The Full Snack Tester (Ben Dowen)

We test software, to gain evidence through observation that help use make judgements about software quality. — The Full Snack Tester (Ben Dowen)

We test software, so we can identify friction and misbehaviours before our users. — The Full Snack Tester (Ben Dowen)

I test for compliance to organizational and regulatory expectations — Perze Ababa

tests help me follow and document where the data flows and what the system does to each data whenever there’s a handoff — Perze Ababa

To be less embarrassed after release. — Lena (Pejgan) Wiberg

To reduce the risk for at least some lawsuits. — Lena (Pejgan) Wiberg

To be able to be able to sleep better at night — Lena (Pejgan) Wiberg

Because it’s really fun, like detective work — Lena (Pejgan) Wiberg

We test, to learn the difference, if any, from how we expect software to behave and how it actually behaves in operation. — The Full Snack Tester (Ben Dowen)

We test software, to investigate potential risks and understand if our mitigation and avoidance of those risks are working. — The Full Snack Tester (Ben Dowen)

I test to understand the product as it exists today. — Chris Kenst

The necessity of a project to test software? To find it's problems. Finding no problems by a certain pattern is also a valid result, just more unlikely to happen.  — ☮️🕊️☯️📢Sebastian, Life Tester [Sebastian linked to a Michael Bolton thread on the topic]

I test mainly to have confidence for refactoring and extension. — Benjamin Bischoff

We test software because we want to learn as much as we can about it and we are specifically keen to find out if there are any potential problems associated with it. — David Högberg

To praraphrase @NicolaLindgren: We test software to be able to affect the perception of the product’s quality. — David Högberg

We test only because the risk of not testing is deemed to high a price to pay — Stu C

I test my code to gain confidence that what it does in reality matches my expectations. — Samuel Nitsche

I do it often as automation to have a signal for unexpected change in the future. — Samuel Nitsche

I do it to document the intentions I had when writing the software. — Samuel Nitsche

To learn something that we want to know — jonhussey

We test to reduce uncertaincy — Declan O'Riordan

We test software to find out if there are differences between the product we’ve got, the product we think we have, and the product we want. — Michael Bolton

Whenever clever people try to do clever things, there's an element of risk. Someone might not understand exactly what the customer and the business want—and the customers or the business might not even know for sure. — Michael Bolton

Programmers might commit errors in implementing the code; smart people make mistakes too. — Michael Bolton

Finding those problems is important when things are serious. When health, life, safety, money, opportunity, reputation — individual and social values — could be at risk. — Michael Bolton [Michael elaborated further in his answer]

To discover the weird and wonderful quirks of the software in question! — Martin Pihl

Testing is a recognition of the fact that 'to err is human' ... The timing of, and degree to which we test, is determined by the potential risk of the change, combined with the impact of what might happen if we don't test. — Parshotam Toora

Entropy. There are an infinite number of ways in which software, that is part of a complex system, can fail. There are only a few ways in which it can succeed. Testing is one approach to find out how it will/can/may fail so you can address that issue approprioately. — Dennis de Booij

We test everything, don’t we? New electronics, relationships, software, habits.. Sort of finding something that you put a value or you will. 😄 — Yasemin Bostancı

We test software to gain confidence on what we are actually doing is what we expected to do as a team. — Trisha Chetani

We test the software because we as a company do not want our customers to find the same issue. — Trisha Chetani

We test software because the company brand name and image are not at stake. We want to convey that our software application requires lower maintenance cost and hence results in more accurate, consistent, and reliable software. — Trisha Chetani

We test software because users can do what they want to do. — Trisha Chetani

We test software because the company can reduce the cost which comes from when people find a lot of issues in production (could be any environment) and are not able to use the software in later stages of the development cycle. — Trisha Chetani

We test software because the company can gain in a way customer satisfaction by producing the quality release of each software version. — Trisha Chetani

We test the software because we enhance the software development process and make it easier for the company to add or remove new features by having confidence. — Trisha Chetani

One of those big questions: “why we develop software “. To serve humanity and us in a symbiotic relationship towards improvement as a race. (Too pophetic for a Sunday 😅). — Robin Gupta

To uncover product and project risk. — Ravi Malayappan

To empirically find out more information about the product. — Ravi Malayappan

In regulatory environments you simply have to do it because the government said so :)! — Ravi Malayappan

Because we want to know where we are with the product to help us make decisions about what to do next with the product. — Pavel Šaman

To increase the quality "hopefully" to reach 5 star product. — Anees Nasry

Emphasize the "SAFE" feeling of customer while using the product. — Anees Nasry

Expand my perspective of how people (Product Owners, Developrs, clients,...) think in different domains. — Anees Nasry

As it's one of the important life's hack (in my humble opinion) — Anees Nasry

Because those involved in software development are wonderful and human and therefore very naturally fallible. — Andrew Kelly

Not being perfect carries risk so we test to discover, investigate and manage that risk. — Andrew Kelly

If you feel pride in the product you want to make sure your end users get the best experience possible. — Georg Neumann

Because developers aren't good testers. :) — Maninder Singh
Image: https://flic.kr/p/4YeBmg