Writing Better Cucumber Scenarios; or, Why We're Deprecating FactoryGirl's Cucumber Steps
For almost three years now, FactoryGirl has provided developers using Cucumber a handful of step definitions that make it easy to create records in the database. Here are a few examples:
Given a post exists with a title of "Blog post about FactoryGirl" Given 5 posts exist Given the following posts exist: | title | author | | FactoryGirl is great! | email: email@example.com | | Ruby is wonderful! | email: firstname.lastname@example.org |
While these steps are very easy to use, it requires a large amount of
knowledge about each model in the step definitions. Your steps now know about
the model name (
title attribute, one of its associations
author has an
Post is a very simple,
straightforward example. Imagine a more complex domain and the amount of
coupling that comes from it when using FactoryGirl's step definitions!
Mike recently wrote about writing steps from the user's perspective and FactoryGirl's step definitions fall into the category of knowing too much about implementation of the application; it doesn't care nearly as much about abstractions, and that's a problem.
As of FactoryGirl 3.5.0, using any of FactoryGirl's generated step definitions will print out a deprecation warning. We'll be removing the step definitions completely in the 4.0.0 release of FactoryGirl in accordance with SemVer. I imagine the existing code will be extracted to a gem similar to Cucumber Rails' training wheels with a nice warning urging developers not to use the the steps.
Here's an example scenario using the step definitions and it rewritten differently to demonstrate the benefits:
# With step definitions Scenario: Complete all incomplete todos Given the following todos exist: | title | author | complete | | Pick up milk | email: email@example.com | false | | Pick up eggs | email: firstname.lastname@example.org | false | And I have signed in as "email@example.com" When I complete the todo "Pick up milk" And I complete the todo "Pick up eggs" Then I should have no incomplete todos
# Without step definitions, but with added clarity Scenario: Complete all incomplete todos Given I have signed in And I have 2 incomplete todos When I complete all my incomplete todos Then I should have no incomplete todos
There are a few differences here. First, because I'm able to title my todos,
there's a bigger tendency to write a step that refers to that title and
complete it. Conceptually, though, completing each one individually and
completing all incomplete are the same. Second, the sign-in flow is
placed before the existence of two incomplete todos. As a stakeholder I
wouldn't think, "Well, in order to see the data, it should exist first!";
it's more likely the thought process of a developer who's familiar with the
four-phase test. Third,
and as I mentioned above, the second scenario now knows nothing about the
objects and attributes explicitly, instead dealing with concepts: "signing
in" (not caring that a user signs in with an email address), "incomplete
todos" (instead of caring about a complete flag on todos), "todos" (instead of
the actual model, which could be named
Notice that the differences here are similar to the changes made to a scenario
relying heavily on Cucumber Rails' old
web_steps.rb (taken from Aslak's
post on the reasons for removing Cucumber Rails' training
Scenario: Successful login Given a user "Aslak" with password "xyz" And I am on the login page And I fill in "User name" with "Aslak" And I fill in "Password" with "xyz" When I press "Log in" Then I should see "Welcome, Aslak"
Scenario: User is greeted upon login Given the user "Aslak" has an account When he logs in Then he should see "Welcome, Aslak"
The first scenario has lots of extra information: password, form labels, button text, current browser location. Gross. The second is much more straightforward, describing concepts instead of page details.
Actively developing a popular testing gem gives thoughtbot an acute advantage of being able to influence the Ruby testing community, for which I'm honored. As such, it's our duty to urge developers to write better software with the help of better tests, and FactoryGirl removing these step definitions is a very real win. Cucumber is meant to describe behavior through interface, not the intracacies of a database; by removing these automatic steps, less brittle steps will be written in their place.