Note: This is a repost from Lars' blog made to widen the reach and hopefully find the right interested parties.


Would you be willing to try Subplot for acceptance testing for one of your real projects, and give us feedback? We're looking for two volunteers.

given a project
when it uses Subplot
then it is successful

Subplot is a tool for capturing and automatically verifying the acceptance criteria for a software project or a system, in a way that's understood by all stakeholders.

In a software project there are always more than one stakeholder. Even in a project one writes for oneself, there are two stakeholders: oneself, and that malicious cretin oneself-in-the-future. More importantly, though, there are typically stakeholders such as end users, sysadmins, clients, software architects, developers, and testers. They all need to understand what the software should do, and when it's in an acceptable state to be put into use: in other words, what the acceptance criteria are.

Crucially, all stakeholders should understand the acceptance criteria the same way, and also how to verify they are met. In an ideal situation, all verification is automated, and happens very frequently.

There are various tools for this, from generic documentation tooling (word processors, text editors, markup languages, etc) to test automation (Cucumber, Selenium, etc). On the one hand, documenting acceptance criteria in a way that all stakeholders understand is crucial: otherwise the end users are at risk of getting something that's not useful to help them, and the project is a waste of everyone's time and money. On the other hand, automating the verification of how acceptance criteria is met is also crucial: otherwise it's done manually, which is slow, costly, and error prone, which increases the risk of project failure.

Subplot aims to solve this by an approach that combines documentation tooling with automated verification.

  • The stakeholders in a project jointly produce a document that captures all relevant acceptance criteria and also describes how they can be verified automatically, using scenarios. The document is written using Markdown.

  • The developer stakeholders produce code to implement the steps in the scenarios. The Subplot approach allows the step implementations to be done in a highly cohesive, de-coupled manner, making such code usually be quite simple. (Test code should be your best code.)

  • Subplot's "docgen" program produces a typeset version as PDF or HTML. This is meant to be easily comprehensible by all stakeholders.

  • Subplot's "codegen" program produces a test program in the language used by the developer stakeholders. This test program can be run to verify that acceptance criteria are met.

Subplot started in in late 2018, and was initially called Fable. It is based on the yarn tool for the same purpose, from 2013. Yarn has been in active use all its life, if not popular outside a small circle. Subplot improves on yarn by improving document generation, markup, and decoupling of concerns. Subplot is not compatible with yarn.

Subplot is developed by Lars Wirzenius and Daniel Silverstone as a hobby project. It is free software, implemented in Rust, developed on Debian, and uses Pandoc and LaTeX for typesetting. The code is hosted on gitlab.com. Subplot verifies its own acceptance criteria. It is alpha level software.

We're looking for one or two volunteers to try Subplot on real projects of their own, and give us feedback. We want to make Subplot good for its purpose, also for people other than us. If you'd be willing to give it a try, start with the Subplot website, then tell us you're using Subplot. We're happy to respond to questions from the first two volunteers, and from others, time permitting. (The reality of life and time constraints is that we can't commit to supporting more people at this time.)

We'd love your feedback, whether you use Subplot or not.