BDD Architecture
BDD automation typically consists of a few layers:
- The natural language steps
- The wiring that ties the steps to their definition
- The step definitions, which usually access page objects
- Page objects, which provide all the capabilities of a page or widget
- Automation over the actual code being exercised, often through the GUI.
The wiring between natural language steps and the step definitions is normally done by the BDD tool (Cucumber).
The automation is normally done using the automation tool (Selenium). Sometimes people do skip the GUI, perhaps targeting an API or the MVC layer instead. It depends how complex the functionality in your web page is. If in doubt, give Selenium a try. I've written automation frameworks for desktop apps; the principle's the same regardless.
Keeping it maintainable
To make the steps easy to maintain and change, keep the steps at a fairly high level. This is frequently referred to as "declarative" as opposed to "imperative". For instance, this is too detailed:
When Fred provides his receipt
And his receipt is scanned
And the cashier clicks "Refund to original card"
And the card is inserted...
Think about what the user is trying to achieve:
When Fred gets a refund to his original card
Generally a scenario will have a few Givens or Thens, but typically only one When (unless you have something like users interacting or time passing, where both events are needed to illustrate the behaviour).
Your page objects in this scenario might well be a "RefundPageObject" or perhaps, if that's too large, a "RefundToCardPageObject". This pattern allows multiple scenario steps to access the same capabilities without duplication, which means that if the way the capabilities are exercised changes, you only need to change them in one place.
Different page objects could also be used for different systems.
Getting started
If you're attacking this for the first time, start by getting an empty scenario that just runs and passes without doing anything (make the steps empty). When you've done this, you'll have successfully wired up Cucumber.
Write the production code that would make the scenario run. (This is the other way round from the way you'd normally do it; normally you'd write the scenario code first. I've found this is a good way to get started though.)
When you can run your scenario manually, add the automation directly to the steps (you've only got one scenario at this point). Use your favourite assertion package (JUnit) to get the outcome you're after. You'll probably need to change your code so that you can automate over it easily, by e.g.: giving relevant test ids to elements in your webpage.
Once you've got one scenario running, try to write any subsequent scenarios first; this helps you think about your design and the testability of what you're about to do. When you start adding more scenarios, start extracting that automation out into page objects too.
Once you've got a few scenarios, have a think about how you might want to address different systems. Avoid using lots of "if" statements if you can; those are hard to maintain. Injecting different implementations of page objects is probably better (the frameworks may well support this by now; I haven't used them in a while).
Keep refactoring as you add more scenarios. If the steps are too big, split them up. If the page objects are too big, divide them into widgets. I like to organize my scenarios by user / stakeholder capabilities (normally related to the "when" but sometimes to the "then") then by different contexts.
So to summarize:
- Write an empty scenario
- Write the code to make that pass manually
- Wire up the scenario using your automation tool; it should now run!
- Write another scenario, this time writing the automation before the production code
- Refactor the automation, moving it out of the steps into page objects
- Keep refactoring as you add more scenarios.
Now you've got a fully wired BDD framework, and you're in a good place to keep going while making it maintainable.
A final hint
Think of this as living documentation, rather than tests. BDD scenarios hardly ever pick up bugs in good teams; anything they catch is usually a code design issue, so address it at that level. It helps people work out what the code does and doesn't do yet, and why it's valuable.
The most important part of BDD is having the conversations about how the code works. If you're automating tests for code that already exists, see if you can find someone to talk to about the complicated bits, at least, and verify your understanding with them. This will also help you to use the right language in the scenarios.
See my post on using BDD with legacy systems for more. There are lots of hints for beginners on that blog too.
