CSC321.01 2016F, Class 13: Behavior-Driven Development ====================================================== _Overview_ * Preliminaries. * Admin. * Upcoming Work. * Questions. * TDD Basics. * BDD Basics. * Cucumber Basics. * A Cucumber Example. * Cucumber in Practice. Preliminaries ------------- ### Admin * Prospective. * Friday PSA. * https://prezi.com/dz6cu1yr83zn/what-does-consent-look-like/ * http://www.theline.org.au/is-this-consent * https://www.youtube.com/playlist?list=PL3xP1jlf1jgJRkChwVOlwQcV0-UqcWiFV * Cash for Dari Barn * I've heard from the SEPC that "CSC 321 feels like CSC 151 in that we're learning things that we'll never use." * I hope that you will learn a lot about software design in this course, and even if you don't use Rails again, the experience of thinking through the steps of building and installing sites will be useful. * Note that the ability to roll out an interactive site in a few hours is a great way to build a portfolio. * And CSC 151 is useful. As a recent alum said "151 teaches you most of the things you should know about Javascript." ### Upcoming Work * Saas HW 2 (Sinatra Hangman) for Monday. (It's in "Intro to BDD, TDD, and SaaS" on the MOOC.) * Readings for Monday: * Don Gotterbarn, Keith Miller, and Simon Rogerson (October 1999). Computer Society and ACM approve Software Engineering Code of Ethics. IEEE Computer 32(10): 84-88. * Peter G. Neumann (February 2015). Inside Risks: Far-sighted thinking about deleterious computer-related events. CACM 58 (2): 30-33. * ACM Council (October 1992). ACM Code of Ethics and Professional Behavior. * Reading Journal for Sunday night at 10pm. (Questions inspired by JLND.) * Subject: Reading Journal for Class 14 (Your Name) * What was the most familiar idea in today's readings on ethics? Where had you seen that idea before? * What surprised you the most in today's readings on ethics? Why was that idea surprising? * Are there ways in which agile practices help support ethical behavior or make it more difficult? * Any other reactions or points you would like to discuss? ### Good Things to Do See * Jazz ensemble tonight at 7:30 in Herrick * Faculty recital Saturday at 7:30 in Bucksbaum * Film plus discussion Saturday at 4:00 in JRC 101. * 1pm Saturday Harris: Howard Hawks' _Bringing up Baby_. ### Questions * Sam needs to talk about scaffolding and proxies and mocks and such for TDD. TDD Basics ---------- * As you design algorithms, you should design tests to make sure that your algorithms work correctly. * And run the tests. * And document your algorithms so that you know what they're supposed to do. * We should write lots of kinds of tests: "Normal" cases, "Edge" cases, "Corner" cases. * Edge and corner cases are things like maximum/minimum. * Multiple kinds of tests * Unit - Individual object, or function or ... * Functional - Ability to perform a subset of tasks * Integration - Ability of the program to form as a whole. * Write clear box tests that ensure that you have code coverage. * We could also write formal proofs that our programs are correct. * One way to test: Print statements or "run the program on this input and read this output". * How does unit testing differ from 161 testing? * It's automated. The test framework either says "All tests passed" or tells you which ones didn't pass. * That means that when you rerun tests it's faster to get them to run the second (and third, and fourth, and fifty-third) time. * We might generate our tests with loops. * If we write tests first, we can check how well we're doing as we go. And we'll kind of know what's wrong. * Humans are lazy and forgetful. They won't keep running all of the tests, either because it takes time or because they don't remember. * Programming as video game. * I passed one test! * I passed two tests! * Game over. You failed. * Goal in most modern languages/environments * A way to specify easily inputs and expected outputs. * A framework that runs those specifications. * Helps you document and think about goals. BDD Basics ---------- * Behavior-driven development. * Take user stories and use them to make SMART goals * SMART = specific, measurable, attainable, relevant, time-bounded * E.g., "As a user of Google I want to log in to Google so that Google can record my every move and thereby give me better advertisements." * More generally, "As a ROLE, I want to ACTION, so that I can GOAL." * Drive your coding based on the stories. That's how you decide what tasks to work on next. * We can write tests based on (very specific) user stories, rather than on individual functions. Cucumber Basics --------------- * BDD framework for Rails (and other systems) * Key idea: The user stories are written in a formal language that is both computer and human readable. * Computer readable: It can be our test (or can be translated into a test). * Human readable: Our clients can read our tests! A Cucumber Example ------------------ 
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 |

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"

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"
Cucumber in Practice -------------------- * 2.5 years ago, when this class started, the alums (and Janet) promoted Cucumber. * Our alums tell me that Cucumber has been less successful than people had expected. * Ideal: Clients can write user stories. * Reality: Clients can read user stories. * Reality: Programmers have to write user stories. * "Natural language" descriptions seem like a good idea, but managing three sets of files (use cases, patterns that translate to real test code, real test code) can be problematic. * Issue: Slow! * Automatic database setup is nice, but there are other Gems, such as FactoryGirl, that also help with database setup. * I will not require you to write explicit Cucumber tests, but I will expect you to write use cases and to write tests (in RSpec or Minitest) that correspond to those use cases. * SS says "We wrote a lot of cucumber tests. It was annoying." How do we run tests when we haven't written the code to test? ------------------------------------------------------------- * Write methods that don't really work. "Stub methods." int square(int x) { return 0; } // STUB assert(square(0) == 0); assert(square(5) == 25); assert(square(INT_MAX) == INT_MAX*INT_MAX); // DUMB TEST assertFailure(square(INT_MAX));