RSpec

# bad
let(:foobar) { blahblah }
let(:baz) { bar }
let(:a) { b }

# good
let(:foobar) { blahblah }
let(:baz)    { bar }
let(:a)      { b }

# bad
let(:foobar) { blahblah }
let(:baz)    { bar }
let(:a)      { b }

# good
let(:foobar) { blahblah }
let(:baz)    { bar      }
let(:a)      { b        }

# bad
describe MyClass do
  before { allow_any_instance_of(MyClass).to receive(:foo) }
end

# good
describe MyClass do
  let(:my_instance) { instance_double(MyClass) }

  before do
    allow(MyClass).to receive(:new).and_return(my_instance)
    allow(my_instance).to receive(:foo)
  end
end

# bad
around do
  some_method
end

around do |test|
  some_method
end

# good
around do |test|
  some_method
  test.call
end

around do |test|
  some_method
  test.run
end

# bad
expect(foo).to be

# good
expect(foo).to be_truthy
expect(foo).to be 1.0
expect(foo).to be(true)

# bad
expect(foo).to eq(true)
expect(foo).to eq(false)
expect(foo).to eq(nil)

# good
expect(foo).to be(true)
expect(foo).to be(false)
expect(foo).to be(nil)

# bad
expect(foo).to eql(1)
expect(foo).to eql(1.0)
expect(foo).to eql(true)
expect(foo).to eql(false)
expect(foo).to eql(:bar)
expect(foo).to eql(nil)

# good
expect(foo).to be(1)
expect(foo).to be(1.0)
expect(foo).to be(true)
expect(foo).to be(false)
expect(foo).to be(:bar)
expect(foo).to be(nil)

# bad
#
# Faster but risk of state leaking between examples
#
describe MyClass do
  before(:all) { Widget.create }
  after(:all) { Widget.delete_all }
end

# good
#
# Slower but examples are properly isolated
#
describe MyClass do
  before(:each) { Widget.create }
  after(:each) { Widget.delete_all }
end

# bad
expect { run }.to change(Foo, :bar).by(0)
expect { run }.to change { Foo.bar }.by(0)

# bad - compound expectations
expect { run }
  .to change(Foo, :bar).by(0)
  .and change(Foo, :baz).by(0)
expect { run }
  .to change { Foo.bar }.by(0)
  .and change { Foo.baz }.by(0)

# good
expect { run }.not_to change(Foo, :bar)
expect { run }.not_to change { Foo.bar }

# good - compound expectations
define_negated_matcher :not_change, :change
expect { run }
  .to not_change(Foo, :bar)
  .and not_change(Foo, :baz)
expect { run }
  .to not_change { Foo.bar }
  .and not_change { Foo.baz }

# bad
context '#foo_bar' do
  # ...
end

context '.foo_bar' do
  # ...
end

# good
describe '#foo_bar' do
  # ...
end

describe '.foo_bar' do
  # ...
end

# bad
describe MyClass, 'do something' do
end

# good
describe MyClass, '#my_instance_method' do
end

describe MyClass, '.my_class_method' do
end

# bad
describe :my_method do
  # ...
end

# good
describe '#my_method' do
  # ...
end

# bad
module MyModule
  RSpec.describe MyClass do
    # ...
  end
end

# good
RSpec.describe MyModule::MyClass do
  # ...
end

# bad
context 'display name presence' do
  # ...
end

# good
describe 'display name presence' do
  # ...
end

# bad
before {}
after do; end
before(:all) do
end
after(:all) { }

# good
before { create_users }
after do
  cleanup_users
end
before(:all) do
  create_feed
end
after(:all) { cleanup_feed }

# bad
RSpec.describe Foo do
  it 'does this' do
  end
  it 'does that' do
  end
end

# good
RSpec.describe Foo do
  it 'does this' do
  end

  it 'does that' do
  end
end

# fair - it's ok to have non-separated one-liners
RSpec.describe Foo do
  it { one }
  it { two }
end

# bad
RSpec.describe Foo do
  describe '#bar' do
  end
  describe '#baz' do
  end
end

# good
RSpec.describe Foo do
  describe '#bar' do
  end

  describe '#baz' do
  end
end

# bad
let(:foo) { bar }
let(:something) { other }
it { does_something }

# good
let(:foo) { bar }
let(:something) { other }

it { does_something }

# bad
before { do_something }
it { does_something }

# bad
after { do_something }
it { does_something }

# bad
around { |test| test.run }
it { does_something }

# good
before { do_something }

it { does_something }

# good
after { do_something }

it { does_something }

# good
around { |test| test.run }

it { does_something }

# bad
subject(:obj) { described_class }
let(:foo) { bar }

# good
subject(:obj) { described_class }

let(:foo) { bar }

# bad
it do
  service = described_class.new
  more_setup
  more_setup
  result = service.call
  expect(result).to be(true)
end

# good
it do
  service = described_class.new
  result = service.call
  expect(result).to be(true)
end

# bad
it 'should find nothing' do
end

# good
it 'finds nothing' do
end

# bad
it 'it does things' do
end

# good
it 'does things' do
end

# bad
it '  has  excessive   spacing  ' do
end

# good
it 'has excessive spacing' do
end

# bad
context '  when a condition   is met  ' do
end

# good
context 'when a condition is met' do
end

# bad
expect(5).to eq(price)
expect(/foo/).to eq(pattern)
expect("John").to eq(name)

# good
expect(price).to eq(5)
expect(pattern).to eq(/foo/)
expect(name).to eq("John")

# bad
before do
  expect(something).to eq 'foo'
end

# bad
after do
  expect_any_instance_of(Something).to receive(:foo)
end

# good
it do
  expect(something).to eq 'foo'
end

# bad
$stdout = StringIO.new
my_app.print_report
$stdout = STDOUT
expect($stdout.string).to eq('Hello World')

# good
expect { my_app.print_report }.to output('Hello World').to_stdout

# bad
whatever_spec.rb         # describe MyClass

# bad
my_class_spec.rb         # describe MyClass, '#method'

# good
my_class_spec.rb         # describe MyClass

# good
my_class_method_spec.rb  # describe MyClass, '#method'

# good
my_class/method_spec.rb  # describe MyClass, '#method'

# bad
describe MyClass, focus: true do
end

describe MyClass, :focus do
end

fdescribe MyClass do
end

# good
describe MyClass do
end

# Bad

it 'checks what foo does' do
  expect(foo).to be
end

before { prepare }
after { clean_up }

# Good
before { prepare }
after { clean_up }

it 'checks what foo does' do
  expect(foo).to be
end

# bad
expect(foo.bar).to eq(foo.bar)
expect(foo.bar).to eql(foo.bar)

# good
expect(foo.bar).to eq(2)
expect(foo.bar).to eql(2)

# bad
subject { -> { do_something } }
it { is_expected.to change(something).to(new_value) }

# good
it 'changes something to a new value' do
  expect { do_something }.to change(something).to(new_value)
end

# bad
it do
  foo = instance_double(Foo).as_null_object
  expect(foo).to have_received(:bar)
end

# good
it do
  foo = instance_spy(Foo)
  expect(foo).to have_received(:bar)
end

# bad
describe MyClass do
  before { @foo = [] }
  it { expect(@foo).to be_empty }
end

# good
describe MyClass do
  let(:foo) { [] }
  it { expect(foo).to be_empty }
end

# bad
it 'validates users' do
  [user1, user2, user3].each { |user| expect(user).to be_valid }
end

# good
it 'validates users' do
  expect([user1, user2, user3]).to all(be_valid)
end

# bad
  let(:params) { blah }
  subject { described_class.new(params) }

  before { do_something }
  subject { described_class.new(params) }

  it { expect_something }
  subject { described_class.new(params) }
  it { expect_something_else }

# good
  subject { described_class.new(params) }
  let(:params) { blah }

# good
  subject { described_class.new(params) }
  before { do_something }

# good
  subject { described_class.new(params) }
  it { expect_something }
  it { expect_something_else }

# Bad
let(:foo) { bar }

it 'checks what foo does' do
  expect(foo).to be
end

let(:some) { other }

it 'checks what some does' do
  expect(some).to be
end

# Good
let(:foo) { bar }
let(:some) { other }

it 'checks what foo does' do
  expect(foo).to be
end

it 'checks what some does' do
  expect(some).to be
end

# Bad
let!(:my_widget) { create(:widget) }

it 'counts widgets' do
  expect(Widget.count).to eq(1)
end

# Good
it 'counts widgets' do
  create(:widget)
  expect(Widget.count).to eq(1)
end

# Good
before { create(:widget) }

it 'counts widgets' do
  expect(Widget.count).to eq(1)
end

# bad
allow(foo).to receive_message_chain(:bar, :baz).and_return(42)

# better
thing = Thing.new(baz: 42)
allow(foo).to receive(:bar).and_return(thing)

# bad
describe do
end

RSpec.describe do
end

# good
describe TestedClass do
end

describe "A feature example" do
end

# bad
describe MyClass, '.do_something' do
end
describe MyClass, '.do_something_else' do
end

# good
describe MyClass do
  describe '.do_something' do
  end
  describe '.do_something_else' do
  end
end

# bad
describe UserCreator do
  it 'builds a user' do
    expect(user.name).to eq("John")
    expect(user.age).to eq(22)
  end
end

# good
describe UserCreator do
  it 'sets the users name' do
    expect(user.name).to eq("John")
  end

  it 'sets the users age' do
    expect(user.age).to eq(22)
  end
end

# bad
describe MyClass do
  let(:foo) { [] }
  let(:bar) { [] }
  let!(:baz) { [] }
  let(:qux) { [] }
  let(:quux) { [] }
  let(:quuz) { {} }
end

describe MyClass do
  let(:foo) { [] }
  let(:bar) { [] }
  let!(:baz) { [] }

  context 'when stuff' do
    let(:qux) { [] }
    let(:quux) { [] }
    let(:quuz) { {} }
  end
end

# good
describe MyClass do
  let(:bar) { [] }
  let!(:baz) { [] }
  let(:qux) { [] }
  let(:quux) { [] }
  let(:quuz) { {} }
end

describe MyClass do
  context 'when stuff' do
    let(:foo) { [] }
    let(:bar) { [] }
    let!(:booger) { [] }
  end

  context 'when other stuff' do
    let(:qux) { [] }
    let(:quux) { [] }
    let(:quuz) { {} }
  end
end

# bad
describe Foo do
  subject(:user) { User.new }
  subject(:post) { Post.new }
end

# good
describe Foo do
  let(:user) { User.new }
  subject(:post) { Post.new }
end

# bad
RSpec.describe User do
  subject { described_class.new }

  it 'is valid' do
    expect(subject.valid?).to be(true)
  end
end

# good
RSpec.describe Foo do
  subject(:user) { described_class.new }

  it 'is valid' do
    expect(user.valid?).to be(true)
  end
end

# also good
RSpec.describe Foo do
  subject(:user) { described_class.new }

  it { is_expected.to be_valid }
end

# bad
context 'when using some feature' do
  let(:some)    { :various }
  let(:feature) { :setup   }

  context 'when user is signed in' do  # flagged by rubocop
    let(:user) do
      UserCreate.call(user_attributes)
    end

    let(:user_attributes) do
      {
        name: 'John',
        age:  22,
        role: role
      }
    end

    context 'when user is an admin' do # flagged by rubocop
      let(:role) { 'admin' }

      it 'blah blah'
      it 'yada yada'
    end
  end
end

# better
context 'using some feature as an admin' do
  let(:some)    { :various }
  let(:feature) { :setup   }

  let(:user) do
    UserCreate.call(
      name: 'John',
      age:  22,
      role: 'admin'
    )
  end

  it 'blah blah'
  it 'yada yada'
end

# bad
let(:foo) { bar }
let(:foo) { baz }

subject(:foo) { bar }
let(:foo) { baz }

let(:foo) { bar }
let!(:foo) { baz }

# good
subject(:test) { something }
let(:foo) { bar }
let(:baz) { baz }
let!(:other) { other }

# bad
describe MyClass do
  it "should be true"
end

describe MyClass do
  it "should be true", skip: true do
    expect(1).to eq(2)
  end
end

describe MyClass do
  it "should be true" do
    pending
  end
end

describe MyClass do
  xit "should be true" do
  end
end

# good
describe MyClass do
end

# bad
expect(foo).to receive(:bar).exactly(1).times
expect(foo).to receive(:bar).exactly(2).times
expect(foo).to receive(:bar).at_least(1).times
expect(foo).to receive(:bar).at_least(2).times
expect(foo).to receive(:bar).at_most(1).times
expect(foo).to receive(:bar).at_most(2).times

# good
expect(foo).to receive(:bar).once
expect(foo).to receive(:bar).twice
expect(foo).to receive(:bar).at_least(:once)
expect(foo).to receive(:bar).at_least(:twice)
expect(foo).to receive(:bar).at_most(:once)
expect(foo).to receive(:bar).at_most(:twice).times

# bad
expect(foo).to receive(:bar).never

# good
expect(foo).not_to receive(:bar)

# bad
RSpec.describe User do
  it 'is valid' do
    # ...
  end

  it 'is valid' do
    # ...
  end
end

# good
RSpec.describe User do
  it 'is valid when first and last name are present' do
    # ...
  end

  it 'is valid when last name only is present' do
    # ...
  end
end

# good
RSpec.describe User do
  it 'is valid' do
    # ...
  end

  it 'is valid', :flag do
    # ...
  end
end

it 'is valid' do
  expect(user).to be_valid
end

it 'validates the user' do
  expect(user).to be_valid
end

# bad
describe 'cool feature x' do
  it { cool_predicate }
end

describe 'cool feature y' do
  it { cool_predicate }
end

# good
describe 'cool feature' do
  it { cool_predicate }
end

describe 'another cool feature' do
  it { another_predicate }
end

# good
context 'when case x', :tag do
  it { cool_predicate }
end

context 'when case y' do
  it { cool_predicate }
end

# good
context Array do
  it { is_expected.to respond_to :each }
end

context Hash do
  it { is_expected.to respond_to :each }
end

# bad
describe 'cool feature' do
  # example group
end

describe 'cool feature' do
  # example group
end

# bad
context 'when case x' do
  # example group
end

describe 'when case x' do
  # example group
end

# good
describe 'cool feature' do
  # example group
end

describe 'another cool feature' do
  # example group
end

# good
context 'when case x' do
  # example group
end

context 'when another case' do
  # example group
end

# bad
describe 'foo' do
  include_examples 'cool stuff'
  include_examples 'cool stuff'
end

# bad
describe 'foo' do
  it_behaves_like 'a cool', 'thing'
  it_behaves_like 'a cool', 'thing'
end

# bad
context 'foo' do
  it_should_behave_like 'a duck'
  it_should_behave_like 'a duck'
end

# good
describe 'foo' do
  include_examples 'cool stuff'
end

describe 'bar' do
  include_examples 'cool stuff'
end

# good
describe 'foo' do
  it_behaves_like 'a cool', 'thing'
  it_behaves_like 'a cool', 'person'
end

# good
context 'foo' do
  it_should_behave_like 'a duck'
  it_should_behave_like 'a goose'
end

# bad
describe Foo do
  let(:foo) { 1 }
  subject { Foo }
  let(:bar) { 2 }
  before { prepare }
  let!(:baz) { 3 }
end

# good
describe Foo do
  subject { Foo }
  before { prepare }
  let(:foo) { 1 }
  let(:bar) { 2 }
  let!(:baz) { 3 }
end

# bad
describe Foo do
  before { setup1 }
  before { setup2 }
end

# good
describe Foo do
  before do
    setup1
    setup2
  end
end

# bad
RSpec.shared_context 'only examples here' do
  it 'does x' do
  end

  it 'does y' do
  end
end

# good
RSpec.shared_examples 'only examples here' do
  it 'does x' do
  end

  it 'does y' do
  end
end

# bad
RSpec.shared_examples 'only setup here' do
  subject(:foo) { :bar }

  let(:baz) { :bazz }

  before do
    something
  end
end

# good
RSpec.shared_context 'only setup here' do
  subject(:foo) { :bar }

  let(:baz) { :bazz }

  before do
    something
  end
end

# bad
it_behaves_like :foo_bar_baz
it_should_behave_like :foo_bar_baz
shared_examples :foo_bar_baz
shared_examples_for :foo_bar_baz
include_examples :foo_bar_baz

# good
it_behaves_like 'foo bar baz'
it_should_behave_like 'foo bar baz'
shared_examples 'foo bar baz'
shared_examples_for 'foo bar baz'
include_examples 'foo bar baz'

# bad
allow(foo).to receive_message_chain(:bar).and_return(42)

# good
allow(foo).to receive(:bar).and_return(42)

# also good
allow(foo).to receive(:bar, :baz)
allow(foo).to receive("bar.baz")

# bad
expect(foo).to receive(:bar).with(42).and_return("hello world")

# good (without spies)
allow(foo).to receive(:bar).with(42).and_return("hello world")
expect(foo).to receive(:bar).with(42)

# bad
let(:subject) { foo }
let!(:subject) { foo }
subject(:subject) { foo }
subject!(:subject) { foo }

# bad
block = -> {}
let(:subject, &block)

# good
subject(:test_subject) { foo }

# bad
describe Article do
  subject(:article) { Article.new }

  it 'indicates that the author is unknown' do
    allow(article).to receive(:author).and_return(nil)
    expect(article.description).to include('by an unknown author')
  end
end

# bad
describe Article do
  subject(:foo) { Article.new }

  context 'nested subject' do
    subject(:article) { Article.new }

    it 'indicates that the author is unknown' do
      allow(article).to receive(:author).and_return(nil)
      expect(article.description).to include('by an unknown author')
    end
  end
end

# good
describe Article do
  subject(:article) { Article.new(author: nil) }

  it 'indicates that the author is unknown' do
    expect(article.description).to include('by an unknown author')
  end
end

# bad
expect {
  raise StandardError.new('error')
}.to raise_error

# good
expect {
  raise StandardError.new('error')
}.to raise_error(StandardError)

expect {
  raise StandardError.new('error')
}.to raise_error('error')

expect {
  raise StandardError.new('error')
}.to raise_error(/err/)

expect { do_something }.not_to raise_error

# bad
let(:foo) do
  double(method_name: 'returned value')
end

# bad
let(:foo) do
  double("ClassName", method_name: 'returned value')
end

# good
let(:foo) do
  instance_double("ClassName", method_name: 'returned value')
end

# bad
expect(something)

# good
expect(something).to be(1)

# bad
allow(foo).to receive(:bar) { |&block| block.call(1) }

# good
expect(foo).to receive(:bar).and_yield(1)