CSC 321.01, Class 14: Behavior-driven design (BDD)

Overview

• Preliminaries
  • Notes and news
  • Upcoming work
  • Questions

News / Etc.

• Sam broke the Web site. Sorry.
• Look over the reading journal assignment for today, but don’t do it.
  • If you want to do it to make up for missing a previous reading journal assignment, that’s fine.
• “Sam, there are all these references to BadSpuds in the SaasBook reading.
  Do we have to do all of the coding for RottenPotatoes?”
  • No way, no how!
  • But that means you have to spend a bit more time reading code whose context is less clear to you.

Upcoming work

• There is a reading journal assignment for Friday.
• You should also do the Sinatra Hangman exercise in SaaSbook/SPOC for Friday.
  • https://github.com/saasbook/hw-sinatra-saas-hangperson

Good things to do

Questions

Behavior Driven Design

• Idea: Write user stories in a way that both programmers and clients can understand. Run those as tests against your code base.
• E.g., “I want users sorted by first name on the ‘list users’ page. If there are multiple users with the same first name, I want them in alphabetical order by last name. For example …”
  • We try to run these as tests.
• In order to do this, we need appropriate tools
  • Have the stories independepent of the testing code.
    • Need to translate from story to code.
    • (Cassie seemed to recmmend this.)
  • Have a system in which the stories are “automatically” translated to test code.
• For the automatic system, we need
  • A standard syntax for expressing the parts of the user story
    • As a ROLE, I want to ACTION so that I can GOAL.
  • A way to parse the non-standard parts of the standard syntax so that you know what’s in the test (Translation of tests to code).
    • Automatic?
    • We write?
    • Both.
  • A library that implements common actions (e.g., “Given these values are in the system.” “When the user clicks on the button labeled ‘Login’”)
    • Capybara provides the latter.
  • Underlying testing system
  • UI
• Cucumber (supposedly) provides all of this
• Cucumber and Capybara and Rails can all be used independently
• It looks really simple; the English tests are really nice to write and to read. The parsing stuff gets more complicated.
• Preset step definitions are sometimes nice.

BDD is a practice

• You are using stories to guide your development.
• You measure progress by the number of stories that pass.
• Important question: “Do my old stories pass?”
  • Too often, adding a new feature breaks something else.
• Good tools show you your progress.
  • Red: Story (or part of your story) does not pass
  • Green: Story (or part thereof) does pass
  • Who cares that Red/Green is the most common form of color blindness, affecting approximately 5% of the population?
  • Shoot for green.

Activity

• Find a project that uses Cucumber.
• Try to find the various parts of the Cucumber tests.
• Be prepared to report back on what you found.
• https://github.com/CSC322-Grinnell/notifications