rspec.md

RSpec

In general, we try to adhere to the BetterSpecs guidelines. This document is a few extensions and key points from that.

Key points

• Make liberal use of describe and context blocks
• Only use the expect and is_expected.to syntax
• Create only the data you need
• In unit tests, avoid touching the database, objects should be built in memory
• Never mock the object under test, only objects which it talks to
• Use shared examples carefully and only where it makes sense. Duplication is far cheaper than the wrong abstraction

Syntax

• let blocks should use multiple line { } proc syntax. { } syntax is less distracting than do end ^[link]

  # Bad
  let(:foo) do
    some_very_long_instantiation
  end
  
  # Good
  let(:bar) {
    some_very_long_instantiation
  }
  
  # Also good
  let(:baz) { 'baz' }

• Use { } blocks for expectations ^[link]

  # bad
  expect do
    something
  end.to change(Something, :else)
  
  # good
  expect { something }.to change(Something, :else)
  
  # also good
  expect {
    something
  }.to change(Something, :else)

• Use do end for before blocks ^[link]

  # bad
  before {
    do_something
  }
  
  # ok
  before { do_something }
  
  # good
  before do
    do_something
  end

  The difference between before and let/expect is due to how it reads. e.g let(:foo) { :bar } reads like 'let foo be equal to bar' whereas before do something; end reads like 'before the test, do this thing'.

• Extract hardcoded values to well-named let blocks, in the same manner as constants ^[link]

  # bad
  expect(1 + 2).to eq(3)
  
  # good
  subject { 1 + 2 }
  let(:expected_result) { 3 }
  
  it { is_expected.to eq(expected_result)}