CSC321.01 2015F, Class 06: Behavior-Driven Development ====================================================== _Overview_ * Preliminaries. * Admin. * Upcoming Work. * Questions. * BDD Basics. * Cucumber Basics. * Some Examples. * Homework time. Preliminaries ------------- ### Admin * We are continuing to hit transition problems. I'll do my best to help you work through them. * Mr. Stone will be teaching next week's class. ### Homework * No matter what it says online, your homework is at . (Agh! I gave you the wrong one for this week. Fortunately, none of you started.) * You will also be doing some readings on computer ethics for next class. Expect an email about that tonight (although I think I've gotten it into the site for now). ### Questions * The only programming homework is hw-bdd-cucumber * The only reading is the ethics readings * Yes, you still have to journal. Behavior-Driven Development --------------------------- * What do you see as the key features of BDD? * What are the relationships you see between BDD and TDD? Similarities and differences? * Some folks have suggested that we replace TDD with BDD. Does that seem like a good idea? Why or why not? Key Features of BDD * A programmatic mechanism for checking whether programs do what people want them to do. * We think about what the program does in terms of overall behavior. ("Big picture") * Typically written in a style that is understandable to non-technical people. Potentially easier to understand. * At least in cucumber, we think about things hierarchically * We break overall utility into features * We break features into scenarios * We break scenarios into steps or declarations * In most BDD systems, we focus on user stories Similarities between BDD and TDD * Both automated ways to check "if things are working right" * Both expect you to express criteria for your tests * Both expect you to write criteria *in advance* of writing code * Both are video games. Turn everything green! Differences between BDD and TDD * Difference audience: TDD tests don't have to be written for non-technical people. * BDD is often big picture, TDD is often smaller pieces. * BDD is a bit easier to tell when you're done. "Look, the user is happy!" * TDD encourages us to focus more on edge cases, whereas BDD is more about general cases (although it does include some edge-like cases) * BDD and TDD give different kinds of confirmation Should we replace TDD with BDD? (or vice versa) As a programmer I want the sqrt function to behave appropriately so that I can write valid code For example, When I give 4 an input to sqrt Then I expect to get 2 as an output When I give -4 as an input to sqrt Then I expect to get 0+2i as an output Wehn I give "frog" as an input to sqrt Then I expect to get an error message check_equal(2, sqrt(4)); check_equal(imaginary(0,2), sqrt(-4)); Arguments for: * You can show your client (or your manager) something that he/she/ze can understand. * Learning one system well is easier than learning two systems well. Arguments against: * We're programmers, we don't need such verbose "code" * BDD seems to have much more running time overhead * Different intent, so use different systems; use things how they are designed. "If all you have is BDD, everything is a behavior." * TDD system features are likely to be different than BDD features; use the things that have the right features. * Don't abuse tools (don't hack things to make them work for something else) * BDD shouldn't be technical testing * Separate domains! * Two ways to think about the example above: Programmer and Client Cucumber -------- * As we think about behaviors, will we need to work on the model, the view, or the controller? * What changes are we likely to have to make? * What step definitions will we have to write to get the text to call Ruby/Rails code? 
Feature: search for movies by director

  As a movie buff
  So that I can find movies with my favorite director
  I want to include and search on director information in movies I enter

Background: movies in database

  Given the following movies exist:
  | title        | rating | director     | release_date |
  | Star Wars    | PG     | George Lucas |   1977-05-25 |
  | Blade Runner | PG     | Ridley Scott |   1982-06-25 |
  | Alien        | R      |              |   1979-05-25 |
  | THX-1138     | R      | George Lucas |   1971-03-11 |
* Model, View, and/or Controller? * Model * View (implicit) * What changes to M, V, C? * Model: Add a new field, Director using the wonders of Migration * View (implicit): You need to be able to see the new field in the listing of movies. * Step definition? movies.each do |movie| addMovie movie.title, movie.rating, ... end 
Scenario: add director to existing movie
  When I go to the edit page for "Alien"
  And  I fill in "Director" with "Ridley Scott"
  And  I press "Update Movie Info"
  Then the director of "Alien" should be "Ridley Scott"
* Model, View, or Controller (plus changes) * View: The edit page needs a text field named "Director". * View: The "Update Movie Info" button might need to be changed. (maybe not, depending on how we phrase the query it makes) * Controller: The update method may need to be changed to include the director. * Model: We changed it above. * Step definition? * /^I go to the edit page for "([^"]*)"$/, should be built into Capabyra. * /^I fill in "([^"]*)" with "([^"]*)"$/, shuld be built into Capabyra. * /^I press "([^"]*)"$/, should be built into Capabyra * Then the director of "Alien" should be "Ridley Scott" * Simple database query 
Scenario: find movie with same director
  Given I am on the details page for "Star Wars"
  When  I follow "Find Movies With Same Director"
  Then  I should be on the Similar Movies page for "Star Wars"
  And   I should see "THX-1138"
  But   I should not see "Blade Runner"

Scenario: can't find similar movies if we don't know director (sad path)
  Given I am on the details page for "Alien"
  Then  I should not see "Ridley Scott"
  When  I follow "Find Movies With Same Director"
  Then  I should be on the home page
  And   I should see "'Alien' has no director info"
Work Time ---------