How can I reuse my gherkin scenarios?

Scenarios are little stories with a basic storyline, a bit like modern Hollywood films. They have a beginning, a middle and an end. The beginning introduces the characters and sets the scene. In the middle, some action happens. Then at the end, the actors achieve their goals and there is a conclusion.

Like a story or film, a scenario should not have a middle and an end followed by another middle and end. Only bad producers trying to milk a franchise do this.

In the example above, we have a feature called "WelcomePage" and a scenario called "Login". The corresponding scenario might look something like this:

This is a little story: it tells how Carlos, a registered user, logs in and is taken to the welcome page. Now we might have other scenarios related to the welcome page, such as that he should see his account balance and unread messages:

But this is clunky - we have already shown that Carlos goes to the welcome page in the previous scenario, so line three is just noise. Maybe we could write this scenario like this:

But now we are missing a key bit of information (that Carlos is on the home page), and including some details that are a bit redundant. We have already established that Carlos needs to log on, so we can safely assume this is the case. Let’s see if we can simplify this a bit:

In this case, the step definition for "When Carlos is on the home page" would include a check to ensure that Carlos has indeed logged on to the application.

And if you wanted to describe several aspects of the home page, you could use a Background clause like this:

Note that scenarios within a feature file are independent - the scenarios in a feature are not meant to be read as a sequence of actions (like episodes of a mini-series) but as independent stories on a related topic (like James Bond films - they all figure the same central character, but the stories are independent of each other). In particular, you should be able to run the scenarios in any order.

Now to get back to the original question - how would you reuse the original scenario "A user logging on the application should be taken to the welcome page" in other scenarios? The answer is, we should never need to. Reuse happens under the hood, in the step definitions. Steps like "And Carlos is on the home page" will call the same underlying code components used by the step definitions for "When Carlos logs on to the application", but readability is king.

Step definition methods are known as "glue code"; this is because they "glue" the step definition phrases to the code that actually does the work. Let me emphasise this point.
Glue code shouldn’t do any direct work. Step definition methods shouldn’t call WebDriver, or invoke a web service, or query a database. They should delegate this work to other, more reusable code.

So reuse comes from the underlying components and individual steps, not from whole scenarios or features. In standard Serenity, for example, this would be done with step libraries. With the more modern Screenplay tests, you would use the more flexible task and interaction classes. But in all cases, the step definition code simply calls other components, and it these components that provide the real reusability.

The reason this sort of question arises is that people often confuse BDD scenarios with test scripts. A BDD scenario is not a test script; it is an executable specification, which is quite a different beast. Using tools like Cucumber to write test scripts almost always results in tests that are hard to read and harder to maintain.

Writing BDD scenarios is a bit of an art. And it's about more than just the scenario-writing - there's a whole process you need to embrace to get optimal results.

If you'd like to understand how to write highly effective BDD Scenarios, ones that can make a real difference in your projects, you need to check out this training course.

This in-depth 4-hour training containing over 30 modules will show you:

• How to get more clarity about the real user requirements sooner (and to uncover the stuff they forgot to tell you!)
• How to leverage your QA skills earlier in the development process, so you stop wasting your time on poorly written requirements and hard-to-test features
• How to facilitate and guide conversations with business folk and other team members more effectively, so that you can uncover edge cases and missing requirements sooner
• How to write powerful and expressive acceptance criteria using Gherkin, the language of tools like Cucumber and SpecFlow
• The five essential qualities of highly effective acceptance criteria

You can check out the training here