RSpec change record matcher

change_record_matcher.rb

# frozen_string_literal: true

# This custom matcher is designed to make record changes easy
#
# Without this matcher you'd typically do one of:
#
#   # I believe these won't always work, depends on object reloading, what is changed, how it's changed,
#   # the order things got loaded, etc.
#   expect { update }.to change(foo, :method)...
#   expect { update }.to change { foo.method }...
#   expect { update }.to change(foo.reload, :method)...
#
#   This will always work
#   expect { update }.to change { foo.reload, :method}...
#
# With this matcher it will automatically reload for you and you can use just it (and chain w/ from/to)
#
#   expect { update }.to change_record(foo, :method)
#   expect { update }.to change_record(foo, :method).from(nil)
#   expect { update }.to change_record(foo, :method).from(nil).to(:bar)
RSpec::Matchers.define :change_record do |record, attribute|
  supports_block_expectations

  match do |block|
    @before = record.reload.send(attribute)
    block.call
    @after = record.reload.send(attribute)
    @before != @after && (@from.nil? || @before == @from) && (@to.nil? || @after == @to)
  end

  chain :from do |value|
    @from = value
  end

  chain :to do |value|
    @to = value
  end

  failure_message do
    message = "expected #{record.class}##{attribute} to change"
    message += " from #{@from}" if @from
    message += " to #{@to}" if @to
    message += ", but it did not"
    message
  end
end