Methods:

expect
.to change { }.by()

describe "#add_task" do 
  it 'only adds a single task' do
    task = Task.new("Feed the cows")
    list = List.new("Stuff")
    
    expect{list.add_task(task)}.to change{list.tasks.length}.by(1)
  end
end

Stub / Mock Example

incomplete_task.stub(:complete?).and_return(false)
# .stub(:method).and_return(what_we_want)

Notes

This test is great because people can change the Task class as much as they want and the test wouldn't change too much.
Good to pick clear variable names, i.e. complete_task / incomplete_task

it "returns only completed tasks" do
  completed_task = mock(:complete_task, :complete? => true)
  incompleted_task = mock(:incompleted_task, :complete? => false)
  
  list = List.new("Stuff", [incomplete_task, completed_task])
  list.completed_tasks.should == [completed_task]
end

Definitions

General Testing

TDD Test Driven Development. Write examples before implementation.
BDD Behaviour-Driven Development is about implementing an application by describing its behavior from the perspective of its stakeholders. (The Rspec Book)
RSpec (mention alternatives, write a simple hand sewn test)

Testing Terms

Structure of an example (test)

Code Example An executable example of how the subject code can be used and its expected behavior. Also called a test, calling tests code examples reinforces the documentation value of RSpec tests.
Example Group defined with the 'describe' method, pass it a string, which is what we'll be describing, this reinforces the idea that Rspec is used to describe and document a system.
It A block which defines a code example

Test Implementation

Expectations A requirement for any test. In code examples we set expectations of what should happen. If the expectations aren't met, the test fails.

  user.active.should == true
  user.active.should eq(true)
  user.active.should be_true
  
  user.favorites.should include("Ramen")
  user.favorites.should_not include("Guava")

Mocks/Doubles/Stubs All the same thing. A test double is an object that stands in for another object in an example (test)
```
  user = mock(:user)
  user = double(:user)
  user = stub(:user)
```

Message Stubs Returning a predefined response to a message within a code example

  user.stub(:name).and_return("Bobby McFerrin")
  user.stub(:name => "Bobby McGee") -- this is working with an actual User object
  user = mock(:user, :name => "Bobby McFerrin") -- this creates a mock user and stub

Chaining Stubs Sometimes you need to stub deep (watch out for this, it's a bad code smell). stub_chain can help:

  user.stub_chain(:account, :billing_address).and_return("717 California St.")
  user.account.billing_address # 717 California St.

Expectations A method stub that will raise an error if it is never called.

user.should_receive(:name).and_return("Bobby McFerrin")

FAQ

Can you TDD when practicing BDD?

Sure. You'll have to circles of Red/Green development. The outer circle, (BDD) and the inner circle (unit testing).

Benefits of TDD

Smaller (shorter) development cycle. Focus on developing and delivering the smallest unit of value (just like your commits!)
Avoid over engineering by writing the simplest code that passes the test when practicing TDD. This discourages you from including rainy day code you might never use.
Develop the interface free of any implementation

Running Thangs

Default rspec output is lame. Make it pretty

rspec --color --format documentation some_spec.rb

Better yet, save this to your ~/.rspec config file:

echo "--color --format documentation" > ~/.rspec

RSpec with Rails

Add rspec-rails to your Gemfile, bundle install then rails generate rspec:install

angiebui/lecture-rspec-examples.md