A Model Student

I've created a state model-based testing tool for the service I work on using Altwalker. I call the tool a walker because it walks the model, interacting with the service as it traverses edges and making assertions about the state in each node.

The service itself is stateless so I've actually been building a model of the kinds of interactions that it allows.

Initially I modelled the journeys our clients make and this was helpful to get a better understanding of our client needs and gripes and also some of the nuances of our API that I hadn't been aware of before.

However, while building and exploring the model I've discovered some other permitted, functional, consistent, but unintended ways to interact with the service.

I decided to keep them in the model because they exist and can be exercised and if their behaviour changes it might tell us we've done something we weren't expecting. But I've been adding configuration options to allow them to be turned off to provide a "vanilla" model when that's desirable.

I had got the model to the point where I thought it covered the key properties of our system when we introduced a new feature. The primary impact of this feature was to add extra data to certain responses.

Naturally, I wanted to use the walker to help me test the feature and, in order to get a feeling for the feature quickly, I wondered how I could do that without needing to change the model and teach the wallker about it.

So I tried making the walker assert that the feature was not seen, which it could do by checking for the presence of a particular field. Then I ran 1000 times against the service.

Inspecting the walker's logs showed that the assertion had fired on 87/1000 runs. Me and the developer sampled from those results and satisfied ourselves that the new data in the response was there legitimately given the request payloads.

I also searched the other 913 logs for payloads that had some of the properties that could invoke the feature and checked that, in those cases, it was correct to not include new data in the response

This was a quick experiment to run, gave some initial reassurance that the right kinds of things were happening, and complemented the other testing that's been done with crafted test cases and exploration using other tools.

If there was any oddity, it was the frequency with which the assertion fired. Intuitively it seemed a little high.

Digging into that I rediscovered that the walker was hard-coding some values that clients would expect to vary and this was biasing the requests in a certain direction.

That was an interesting result from a testing perspective because it suggested a way that I could control the system behaviour outside of the normal range of usage.

So I added a parameter to the walker's configuration file to let that value be set but had it default to simulate what our clients would do.

Testing is learning, they say. And they're right, but it's not just learning about the system under test. In this experiment I learned, for example:

a way to exploit the walker for faster feedback.
a way to control the behaviour of the walker to provoke a particular effect.
that the approach I've taken to configuration is probably not going to be flexible enough.

Image: https://flic.kr/p/ZmQyVu

Comments

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 answ...

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 ...

The Best Programmer Dan Knows

I was pairing with my friend Vernon at work last week, on a tool I've been developing. He was smiling broadly as I talked him through what I'd done because we've been here before. The tool facilitates a task that's time-consuming, inefficient, error-prone, tiresome, and important to get right. Vern knows that those kinds of factors trigger me to change or build something, and that's why he was struggling not to laugh out loud. He held himself together and asked a bunch of sensible questions about the need, the desired outcome, and the approach I'd taken. Then he mentioned a talk by Daniel Terhorst-North, called The Best Programmer I Know, and said that much of it paralleled what he sees me doing. It was my turn to laugh then, because I am not a good programmer, and I thought he knew that already. What I do accept, though, is that I am focussed on the value that programs can give, and getting some of that value as early as possible. He sent me a link to the ta...

Beginning Sketchnoting

In September 2017 I attended Ian Johnson 's visual note-taking workshop at DDD East Anglia . For the rest of the day I made sketchnotes, including during Karo Stoltzenburg 's talk on exploratory testing for developers (sketch below), and since then I've been doing it on a regular basis. Karo recently asked whether I'd do a Team Eating (the Linguamatics brown bag lunch thing) on sketchnoting. I did, and this post captures some of what I said. Beginning sketchnoting, then. There's two sides to that: I still regard myself as a beginner at it, and today I'll give you some encouragement and some tips based on my experience, to begin sketchnoting for yourselves. I spend an enormous amount of time in situations where I find it helpful to take notes: testing, talking to colleagues about a problem, reading, 1-1 meetings, project meetings, workshops, conferences, and, and, and, and I could go on. I've long been interested in the approaches I've evol...

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...

ChatGPTesters

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-- "Why don’t we replace the testers with AI?" We have a good relationship so I feel safe telling you that my instinctive reaction, as a member of the T...

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 gener...

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...

Express, Listen, and Field

Last weekend I participated in the LLandegfan Exploratory Workshop on Testing (LLEWT) 2024, a peer conference in a small parish hall on Anglesey, north Wales. The topic was communication and I shared my sketchnotes and a mind map from the day a few days ago. This post summarises my experience report. Express, Listen, and Field Just about the most hands-on, practical, and valuable training I have ever done was on assertiveness with a local Cambridge coach, Laura Dain . In it she introduced Express, Listen, and Field (ELF), distilled from her experience across many years in the women’s movement, business, and academia. ELF: say your key message clearly and calmly, actively listen to the response, and then focus only on what is relevant to your needs. I blogged a little about it back in 2017 and I've been using it ever since. Assertiveness In a previous role, I was the manager of a test team and organised training for the whole ...

Hiccupps

Search This Blog