What is difference of Rails + rspec let VS let! (bang or not bang?) :

require "rails_helper"

# There cases all pass
describe do
  context do
    let!(:user) { create :user, name: 'Alice' }

    # it create a record before expect "user" in spec
    it do
      expect(User.count).to eq 1
      expect(user.name).to eq 'Alice'
      expect(User.count).to eq 1
    end
  end

  context do
    let(:user) { create :user, name: 'Bob' }

    # it does not create a record before expect "user" in spec
    it do
      expect(User.count).to eq 0
      expect(user.name).to eq 'Bob'
      expect(User.count).to eq 1
    end
  end
end

describe do
  context do
    # Let bang and same let names
    # It does not create three records
    # only last let! evaluated
    let!(:user) { create :user, name: 'Alice' }
    let!(:user) { create :user, name: 'Bob' }
    let!(:user) { create :user, name: 'Carol' }

    it do
      expect(User.count).to eq 1
      expect(user.name).to eq 'Carol'
      expect(User.count).to eq 1
    end
  end

  context do
    # Different let names
    # It create each three records
    let!(:user1) { create :user, name: 'Alice' }
    let!(:user2) { create :user, name: 'Bob' }
    let!(:user3) { create :user, name: 'Carol' }

    it do
      expect(User.count).to eq 3
      expect(user1.name).to eq 'Alice'
      expect(user2.name).to eq 'Bob'
      expect(user3.name).to eq 'Carol'
      expect(User.count).to eq 3
    end
  end
end

Original by Github issue

https://github.com/YumaInaura/YumaInaura/issues/2851

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公開日時

2019-12-17