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. https://www.computer.org/cms/Computer.org/Publications/code-of-ethics.pdf
  • Peter G. Neumann (February 2015). Inside Risks: Far-sighted thinking about deleterious computer-related events. CACM 58 (2): 30-33. http://www.csl.sri.com/users/neumann/cacm235.pdf
  • ACM Council (October 1992). ACM Code of Ethics and Professional Behavior. http://www.acm.org/about/code-of-ethics/
• 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 http://www.cs.grinnell.edu/~rebelsky/s2d@g/

• 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));