stubs_mocks.rb

class User
  # justin rarely mutates initially set instance variables
  attr_reader :first_name, :last_name, :birth_date

  def initialize(first_name, last_name, birth_date=nil)
    @first_name = first_name
    @last_name = last_name
    @birth_date = birth_date
  end

  def full_name
    "#{first_name} #{last_name}"
  end

  def age
    bday = Date.parse(birth_date)
    today = Date.today
    ((today - bday)/365).to_i
  end
end

# note, a big take away is that we're not stubbing the current object.
# stub externals, in this case the Date class
describe User do
  let(:today) { Date.parse("2014-05-08") }
  let(:user) { User.new("Dave", "Mox", "05/05/1989") }

  before do
    # Date.stub(:today).and_return(date)
    Date.stub(today: today) # equivalent to above
  end

  it "has an age" do
    expect(user.age).to eq(25)
  end

  context "last year" do
    let(:today) { Date.parse("2013-05-08") }

    it "was one year younger" do
      # Date.stub(:today).and_return(date)
      expect(user.age).to eq(24)
    end
  end
end

# with Objects
describe User do
  it "has a first_name" do
    user = User.new("Dave", "Mox")
    expect(user.first_name).to eq("Dave")
  end

  it "has a last name" do
    user = User.new("Dave", "Mox")
    expect(user.last_name).to eq("Mox")
  end

  it "has a full name" do
    user = User.new("Dave", "Mox")
    expect(user.full_name).to eq("Dave Mox")
  end
end

# with Test Doubles
# A test double is an object that stands in for another object in your system
# during a code example. Use the double method, passing in an optional
# identifier, to create one.
describe User do
  it "has a first_name" do
    # newest version of RSpec makes #instance_double available.
    user = double("User", first_name: "Dave")
    expect(user.first_name). to eq("Dave")
  end

  it "has a last_name" do
    user = double("User", last_name: "Mox")
    expect(user.last_name). to eq("Mox")
  end
end

# with Method Stubs
# A method stub is an implementation that returns a pre-determined value. Method
# stubs can be declared on test doubles or real objects using the same syntax.
describe User do
  it "has a full_name" do
    user = double("User")
    user.stub(:full_name).and_return("Dave Mox")
    expect(user.full_name).to eq("Dave Mox")
  end
end

# create test double and declare method stub in one statement
describe User do
  it "has a full_name" do
    user = double("User", full_name: "Dave Mox")
    expect(user.full_name).to eq("Dave Mox")
  end
end