ChainChecker is used when you want to group multiple `expect`.

chain_checker.rb

# frozen_string_literal: true

##
# {ChainChecker} is used when you want to group multiple `expect`.
# You use it including in `RSpec::Matchers.define` block.
#
#    RSpec::Matchers.define :have_foo_bar do |foo, bar|
#      include ChainChecker
#    end
#
# The block passed to the main method becomes the entry point.
#
#    RSpec::Matchers.define :have_foo_bar do |foo, bar|
#      include ChainChecker
#
#      main do |actual|
#        expect(actual.foo).to eq foo
#        expect(actual.bar).to eq bar
#      end
#    end
#
# If you use `expect` in the `match` method, the error messages are very inconvenient, but the error that occurs within the `main` method will display user-friendly messages.  
# The test code is as follows.
#
#    context 'some' do
#      it 'should have foo and bar' do
#        some = Some.find(1)
#        expect(some).to have_foo_bar('foo value', 'bar value')
#      end
#    end
#
# If you want to do additional tests, you can chain them with chain methods.  
# Using the check block in the chain method, you can write the test more naturally.
#
#    RSpec::Matchers.define :have_foo_bar do |foo, bar|
#      include ChainChecker
#
#      chain :with_baz_qux do |baz, qux|
#        check do |actual|
#          expect(actual.baz).to eq baz
#          expect(actual.qux).to eq qux
#        end
#      end
#    end
#
# The test code is as follows.
#
#    context 'some value' do
#      it 'should have foo and bar' do
#        some = Some.find(1)
#        expect(some).to have_foo_bar('foo value', 'bar value').with_baz_qux('baz value', 'qux value')
#      end
#    end
#
module ChainChecker
  def self.included(base)
    base.define_singleton_method :main do |options = {}, &main_block|
      match options do |actual|
        instance_exec(actual, &main_block)
        execute_chain_checks(actual)
      rescue RSpec::Expectations::ExpectationNotMetError => e
        failure_position = e.backtrace.find {|path| path.exclude?('/lib/ruby/gems/') }
        @failure_message = "#{e.message}\nat #{failure_position}"
        false
      end
    end

    base.failure_message do |_|
      @failure_message
    end
  end

  def check(&block)
    checks << block
  end

  private

    def checks
      @checks ||= []
    end

    def execute_chain_checks(actual)
      checks.each do |block|
        block.call(actual)
      end
    end
end