Skip to main content

The Anatomy of a Definition of Testing

At CEWT 3 I offered a definition of testing up for discussion. This is it:
Testing is the pursuit of actual or potential incongruity
As I said there, I was trying to capture something of the openness, the expansiveness of what testing is for me: there is no specific technique; it is not limited to the software; it doesn't have to be linear; there don't need to be requirements or expectations; the same actions can contribute to multiple paths of investigation at the same time; it can apply at many levels and those levels can be distinct or overlapping in space and time.
And these are a selection of the comments and questions that it prompted before, during and after the event, loosely grouped:

Helicopter view

  • it is sufficiently open that people could buy into it, and read into it, particularly non-testers.
  • it's accurate and to the point.
  • it has the feel of Weinberg's definition of a problem. 
  • it sounds profound but I'm not sure whether there is any depth.
  • it seems very close to the regular notion of targeting information/unknowns.


  • can not testing be part of this idea of testing?
  • how does the notion of tacit testing (from CEWT 3 discussion) fit in?
  • Kaner talks about balancing freedom and responsibility in testing. Is that covered here?
  • the definition doesn't talk about risk.

Practical utility

  • it couldn't be used to help someone new to testing decide what to do when testing.
  • I could imagine putting this onto a sticky and trying to align my actions with it.


  • what do you mean by pursuit
  • incongruity is too complex a word.
  • what other words could replace testing in the definition and it still hold?
  • when I see or I wonder about whether it's exclusive (in the Boolean sense).

In this post I'm going to talk about just the words. I spent a deal of time choosing my words - and that in itself is a warning sign. If I have to graft to find words whose senses are subtly tuned to achieve just the interpretation that I want, then I worry that others will easily have a different interpretation.

And, despite this being a definition of testing for me, it's interesting to observe how often I appeal to my feelings and desires in the description below. Could the degree of personal investment compromise the possibility of it having general appeal or utility, I wonder.


Other definitions use words like search, explore, evaluate, investigate, find out, ... I was particularly keen to find a verb that captured two aspects of testing for me: finding out what is there, and digging into what has been found.

What I like about pursuit is that it permits (at least to me) both, and additionally conveys a sense of chasing something which might be elusive, itinerant, latent or otherwise hard to find. Oxford Dictionaries has these definitions, amongst others of pursue:
  • follow or chase (someone or something)
  • continue to investigate or explore (an idea or argument)

These map onto my two needs in ways that other verbs don't:
  • search: feels more about the former and less about the latter.
  • investigate: feels more natual when there's a thing to investigate.
  • explore: could possibly do duty for me (and it's popular in testing definitions) but exploratory testing can be perceived as cutting out other kinds of testing and I don't want that interpretation.
  • evaluate: needs data; pursuit can gather data.
  • find out: feels like it has finality in it. To reflect the fact that testing is unlikely to be complete I'd want to say something like "Testing is the attempt to find out about actual or potential incongruity"


As one of the criticisms of my definition points out, this word is not part of most people's standard lexicon. Oxford Dictionaries says that it means this:
 Not in harmony or keeping with the surroundings or other aspects of something.
I like it because it permits nuance in the degree to which something needs to be out of place: it could be completely wrong, or just feel a bit odd in its context. But the price I pay for the nuance is the lack of common currency. On balance I accepted this in order to keep the definition short.

"actual or potential"

I felt unhappy with a definition that didn't include this, such as:
Testing is the pursuit of incongruity
because I wanted testing's possibilities to include suggesting that there might be a problem. If the definition of incongruity I am using permitted possible disharmony then I'd have been happier with this shorter variant.

I have subsequently realised that I am, to some extent, reflecting a testing/checking distinction here too: a check with fixed expectations can find actual incongruity while testing could in addition find potential incongruity.

However, the entire definition is, for me, in the context of the relative rule - so any incongruities of any kind are tied to a context, person, time - and also the need to govern the actions in the pursuit by some notions of what is important to the people who are important to whatever is being tested.

But, even given that, I still find it hard to accept the definition without potential. Perhaps because it flags the lack of certainty inherent in much testing.

Edit: Olekssii Burdin wrote his own definition of testing after reading this, and Harnessed Tester offers his here too.


  1. Hi James,
    You've said that this is a definition for you, so I'd say it's perfectly logical to encompass, within the stated definition of "incongruity", your own internal source of dissonance that inspires the "Is there a problem here" question in the first place. In that sense the distinction is not between actual and potential as a property of the incongruity. It is, as you noted, a distinction in terms of the perception of the incongruity.

    1. Hi Dan,

      I've been thinking some more about "actual or potential" and wondering whether I'd be comfortable instead with "relevant" which (a) removes the clumsiness and (b) brings in an element of the subjective nature.

  2. Thank you James,
    I find your definition quite romantic. But this makes it inspiring :-)
    And I translated my post to English
    Thank you for commenting it!


Post a Comment

Popular posts from this blog

Notes on Testing Notes

Ben Dowen pinged me and others on Twitter last week , asking for "a nice concise resource to link to for a blog post - about taking good Testing notes." I didn't have one so I thought I'd write a few words on how I'm doing it at the moment for my work at Ada Health, alongside Ben. You may have read previously that I use a script to upload Markdown-based text files to Confluence . Here's the template that I start from: # Date + Title # Mission # Summary WIP! # Notes Then I fill out what I plan to do. The Mission can be as high or low level as I want it to be. Sometimes, if deeper context might be valuable I'll add a Background subsection to it. I don't fill in the Summary section until the end. It's a high-level overview of what I did, what I found, risks identified, value provided, and so on. Between the Mission and Summary I hope that a reader can see what I initially intended and what actually

69.3%, OK?

The Association for Software Testing is crowd-sourcing a book, Navigating the World as a Context-Driven Tester , which aims to provide responses to common questions and statements about testing from a context-driven perspective . It's being edited by Lee Hawkins who is posing questions on Twitter ,  LinkedIn ,  Slack , and the AST mailing list and then collating the replies, focusing on practice over theory. I've decided to contribute by answering briefly, and without a lot of editing or crafting, by imagining that I'm speaking to someone in software development who's acting in good faith, cares about their work and mine, but doesn't have much visibility of what testing can be. Perhaps you'd like to join me?   --00-- "What percentage of our test cases are automated?" There's a lot wrapped up in that question, particularly when it's a metric for monitoring the state of testing. It's not the first time I've been asked either. In my

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 . --00-- 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 —

Testing is Knowledge Work

  The Association for Software Testing is crowd-sourcing a book, Navigating the World as a Context-Driven Tester , which aims to provide responses to common questions and statements about testing from a context-driven perspective . It's being edited by Lee Hawkins who is posing questions on Twitter ,  LinkedIn ,  Slack , and the AST mailing list and then collating the replies, focusing on practice over theory. I've decided to contribute by answering briefly, and without a lot of editing or crafting, by imagining that I'm speaking to someone in software development who's acting in good faith, cares about their work and mine, but doesn't have much visibility of what testing can be. Perhaps you'd like to join me?   --00-- "We need some productivity metrics from testers" OK. I'd like to help you meet your need if I can but to do that I'll need to ask a few questions. Let's start with these: Who needs the metrics? Is there a particular pr

My Favourite Tool

Last week I did a presentation to a software testing course at EC Utbildning in Sweden titled Exploring with Automation where I demoed ways in which I use software tools to help me to test. Following up later, one of the students asked whether I had a favourite tool. A favourite tool? Wow, so simple but sooo deep!  Asking for a favourite tool could make a great interview question, to understand the breadth and depth of a candidate's knowledge about tools, how they think about an apparently basic request with deep complexity beneath (favourite for what task, on what basis, in what contexts, over what timescale?  what is a tool anyway?) and how they formulate a response to take all of that into account. I could truthfully but unhelpfully answer this question with a curt Yes or No. Or I could try and give something more nuanced. I went for the latter. At an extremely meta level I would echo Jerry Weinberg in Perfect Software : The number one te

Enjoy Testing

  The testers at work had a lean coffee session this week. One of the questions was  "I like testing best because ..." I said that I find the combination of technical, intellectual, and social challenges endlessly enjoyable, fascinating, and stimulating. That's easy to say, and it sounds good too, but today I wondered whether my work actually reflects it. So I made a list of some of the things I did in the last working week: investigating a production problem and pairing to file an incident report finding problems in the incident reporting process feeding back in various ways to various people about the reporting process facilitating a cross-team retrospective on the Kubernetes issue that affected my team's service participating in several lengthy calibration workshops as my team merges with another trying to walk a line between presenting my perspective on things I find important and over-contributing providing feedback and advice on the process identifying a

Trying to be CEWT

I attend, enjoy, hopefully contribute to, and get a lot from, the local tester meetups and Lean Coffee  in Cambridge. But I'd had the thought kicking around for a long time that I'd like to try a peer workshop inspired by MEWT , DEWT , LEWT and the like. I finally asked a few others, including the local meetup organisers, and got mostly positive noises, so I decided to give it a go. I wrote a short statement to frame the idea, based on LEWT's: CEWT ( Cambirdge Exploratory Workshop on Testing ) is an exploratory peer workshop. We take the view that discussions are more interesting than lectures. We enjoy diverse ideas, and limit some activities in order to work with more ideas. and proposed a mission for an initial attempt to validate it locally on a small scale. Other local testers helped to refine the details in usual the testing ways - you know: criticism, questions, thought experiments, challenges, comparisons, mockery and the rest - and a list of potential at

Testing and Words

  The other day I got tagged on a Twitter thread started by Wicked Witch of the Test about people with a background in linguistics who’ve ended up in testing. That prompted me to think about the language concepts I've found valuable in my day job, then I started listing them, and then realised how many of them I've mentioned here over the years .   This post is one of an occasional series collecting some of those thoughts.  --00-- In The Complete Plain Words , Ernest Gowers notes, acidly, that: What appears to be a sloppy or meaningless use of words may well be a completely correct use of words to express sloppy or meaningless ideas. It surely sounds trite to say it but our choice of words can make a significant difference to how well our message is understood, and how we are judged. We choose from amongst those words we know, our lexicons . The more my lexicon agrees with yours, the greater our chance of us achieving a shared understanding when we converse. But lexic

The Ideal Test Plan

A colleague pinged me the other day, asking about an "ideal test plan" and wondering whether I could suggest something. Not without a bit more information, I said. OK, they said. Who needs the plan, for what purpose? I asked. Their response: it's for internal use, to improve documentation, and provide a standard structure. We work in a medical context and have strict compliance requirements, so I wondered aloud whether the plan is needed for audit, or to show to customers? It's not, they replied, it's just for the team. Smiling now, I stopped asking questions and delivered the good news that I had what they were looking for. Yes? they asked, in anticipation. Naturally I paused for dramatic effect and to enhance the appearance of deep wisdom, before saying: the ideal plan is one that works for you. Which is great and all that, but not heavy on practical advice. --00-- I am currently running a project at the Association for Software Testing and there is a plan for

Use the Force Multiplier

On Fridays I pair with doctors from Ada 's medical quality team. It's a fun and productive collaboration where I gain deeper insight into the way that diagnostic information is encoded in our product and they get to see a testing perspective unhindered by domain knowledge. We meet at the same time each week and decide late on our focus, choosing something that one of us is working on that's in a state where it can be shared. This week we picked up a task that I'd been hoping to get to for a while: exploring an API which takes a list of symptoms and returns a list of potential medical conditions that are consistent with those symptoms.  I was interested to know whether I could find small input differences that led to large output differences. Without domain knowledge, though, I wasn't really sure what "small" and "large" might mean. I prepared an input payload and wrote a simple shell script which did the following: make a