Test Cookbook

RSpec

Getting started.

Install rspec gem using gem command.

Terminal

$ gem install rspec

If you like to use bundler you can setup a Gemfile to look like.

Gemfile

source "https://rubygems.org"
gem "rspec"

Your First test.

Lets say that we want to test a class that adds up numbers and has a function total. That function could look like.

class Adder
  def initialize(a, b)
    @a = a
    @b = b
  end

  def total
    @a + @b
  end
end

Now that we have what we are going to test. We need to have a basic layout of our test ready.

RSpec.describe Adder do
  describe "adds numbers" do
    it "Adder total returns correct value" do

    end
  end
end

Notice that RSpec works in a describe and it format. The first section tells RSpec that we are going to test the Adder function. The second describe tells a high level story of what it will cover. Lastly the “it” will test a specific functionality that is a part of the describe.

Next we need to load up a couple of numbers to the Adder function and then create an assertion to what the correct total.

RSpec.describe Adder do
  describe "adds numbers" do
    it "Adder total returns correct value" do
        adder = Adder.new(3,5)
        expect(adder.total).to eq(8)
    end
  end
end

See it all together

spec.rb

class Adder
  def initialize(a, b)
    @a = a
    @b = b
  end

  def total
    @a + @b
  end
end

RSpec.describe Adder do
  describe "adder" do
    it "Adder total returns correct value" do
      adder = Adder.new(3,5)
      expect(adder.total).to eq(8)
    end
  end
end

Run your test

Terminal

$ rspec spec.rb
.

Finished in 0.00091 seconds (files took 0.09214 seconds to load)
1 example, 0 failures