It's Great to Mutate

The product I'm working on at the moment is a Ada, a symptom checking app. The basic idea is that users enter a few details about themselves and their current symptoms and are then guided through a series of questions which leads to them being given a list of probability-ranked conditions they might have based on their answers.

As you'd expect in this field, with this kind of data, a lot of care and concern is taken to understand how the app performs and what caused any changes in that performance across releases. There are many layers of testing.

In one of those layers we have medical test cases. (And these are literally cases in the medical sense.) Each one represents data about an individual who might present to a doctor with a particular set of symptoms, a given medical history, possible comorbidities and so on. Each also comes with a set of acceptable condition suggestions and other expectations about how the software should behave when asking this kind of user questions.

My team has recently merged with another and taken over responsibility for the software that runs these test cases. This made me happy: a test runner is an attack vector for testing!

Having learned how the runner works, in the last couple of weeks I've been pairing with our medical staff, using the test cases and the runner to get "landscape views" of the performance of our software.

How? By taking a single test case and mutating it systematically on a handful of variables to generate loads of variant cases differing from one another only slightly, but predictably.

To take a simple example, let's say I have a test case that describes a 10-year-old boy with a nominated illness. I might generate 100 versions of that case that change only the age, i.e. the same case data for a male of age one, two, three, and so on up to 100 years. I'd then run them, parse the results of each case, and load it into a spreadsheet for analysis.

The obfuscated screenshot at the top is an example of one such experiment. The expected most likely condition is highlighted in green. Sorting and filtering the data shows that its position in the list of suggestions is invariant except for a few places, shown in the rows near the top of the image.

That's interesting to the doctors, and it's also very easy to look for and highlight in this kind of view.

Maybe you are thinking that equivalence classes might have observed the same. Well you're right ... they might. But when the software under test is complex and likely to exhibit emergent behaviour, this kind of approach, making many small variations in inputs and comparing the outputs in bulk to identify patterns or outliers, can be a productive way to look for places to dig into.

The approach feels like a close relative of metamorphic testing. There's nothing particularly complex about it either. I have a couple of bash scripts that mangle the data on the way in and collate it on the way out and the test runner itself just does what it always did.

It's great to mutate the title says, and it's right, but I also love exploiting existing test data and infrastructure to ask new questions.

Comments

Can Code, Can't Code, Is Useful

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 , Mastodon , 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-- "If testers can’t code, they’re of no use to us" My first reaction is to wonder what you expect from your testers. I am immediately interested in your working context and the way

Meet Me Halfway?

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 , Mastodon , 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-- "Stop answering my questions with questions." Sure, I can do that. In return, please stop asking me questions so open to interpretation that any answer would be almost meaningless and certa

Not Strictly for the Birds

One of my chores takes me outside early in the morning and, if I time it right, I get to hear a charming chorus of birdsong from the trees in the gardens down our road, a relaxing layered soundscape of tuneful calls, chatter, and chirrupping. Interestingly, although I can tell from the number and variety of trills that there must be a large number of birds around, they are tricky to spot. I have found that by staring loosely at something, such as the silhouette of a tree's crown against the slowly brightening sky, I see more birds out of the corner of my eye than if I scan to look for them. The reason seems to be that my peripheral vision picks up movement against the wider background that direct inspection can miss. An optometrist I am not, but I do find myself staring at data a great deal, seeking relationships, patterns, or gaps. I idly wondered whether, if I filled my visual field with data, I might be able to exploit my peripheral vision in that quest. I have a wide monito

Postman Curlections

My team has been building a new service over the last few months. Until recently all the data it needs has been ingested at startup and our focus has been on the logic that processes the data, architecture, and infrastructure. This week we introduced a couple of new endpoints that enable the creation (through an HTTP POST) and update (PUT) of the fundamental data type (we call it a definition ) that the service operates on. I picked up the task of smoke testing the first implementations. I started out by asking the system under test to show me what it can do by using Postman to submit requests and inspecting the results. It was the kinds of things you'd imagine, including: submit some definitions (of various structure, size, intent, name, identifiers, etc) resubmit the same definitions (identical, sharing keys, with variations, etc) retrieve the submitted definitions (using whatever endpoints exist to show some view of them) compare definitions I submitted fro

Testers are Gate-Crashers

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 , Mastodon , 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-- "Testers are the gatekeepers of quality" Instinctively I don't like the sound of that, but I wonder what you mean by it. Perhaps one or more of these? Testers set the quality sta

Vanilla Flavour Testing

I have been pairing with a new developer colleague recently. In our last session he asked me "is this normal testing?" saying that he'd never seen anything like it anywhere else that he'd worked. We finished the task we were on and then chatted about his question for a few minutes. This is a short summary of what I said. I would describe myself as context-driven . I don't take the same approach to testing every time, except in a meta way. I try to understand the important questions, who they are important to, and what the constraints on the work are. With that knowledge I look for productive, pragmatic, ways to explore whatever we're looking at to uncover valuable information or find a way to move on. I write test notes as I work in a format that I have found to be useful to me, colleagues, and stakeholders. For me, the notes should clearly state the mission and give a tl;dr summary of the findings and I like them to be public while I'm working not just w

Build Quality

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 , Mastodon , 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-- "When the build is green, the product is of sufficient quality to release" An interesting take, and one I wouldn't agree with in general. That surprises you? Well, ho

Make, Fix, and Test

A few weeks ago, in A Good Tester is All Over the Place , Joep Schuurkes described a model of testing work based on three axes: do testing yourself or support testing by others be embedded in a team or be part of a separate team do your job or improve the system It resonated with me and the other testers I shared it with at work, and it resurfaced in my mind while I was reflecting on some of the tasks I've picked up recently and what they have involved, at least in the way I've chosen to address them. Here's three examples: Documentation Generation We have an internal tool that generates documentation in Confluence by extracting and combining images and text from a handful of sources. Although useful, it ran very slowly or not at all so one of the developers performed major surgery on it. Up to that point, I had never taken much interest in the tool and I could have safely ignored this piece of work too because it would have been tested by

The Best Laid Test Plans

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 , Mastodon , 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's the best format for a test plan?" I'll side-step the conversation about what a test plan is and just say that the format you should use is one that works for you, your coll

Test Now

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 , Mastodon , 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-- "When is the best time to test?" Twenty posts in , I hope you're not expecting an answer without nuance? You are? Well, I'll do my best. For me, the best time to test is when there

Hiccupps

Search This Blog