require_relative "helper"

benchmark_allocations do
  1000.times do |i|
    RSpec.describe "group #{i}" do
      it "has one example" do
      end
    end
  end
end

__END__

Original allocations:

               class_plus                 count
----------------------------------------  -----
String                                    28000
Array                                     15000
RubyVM::Env                                9000
Proc                                       9000
Hash                                       9000
RSpec::Core::Hooks::HookCollection         6000
Array<String>                              5000
MatchData                                  3000
Array<String,Fixnum>                       2000
Array<Module>                              2000
Module                                     2000
RSpec::Core::Example::ExecutionResult      2000
RSpec::Core::Metadata::ExampleGroupHash    1000
Class                                      1000
Array<Hash>                                1000
RSpec::Core::Hooks::AroundHookCollection   1000
RSpec::Core::Hooks::HookCollections        1000
RSpec::Core::Metadata::ExampleHash         1000
RSpec::Core::Example                       1000
Array<RSpec::Core::Example>                1000


After removing `:suite` support from `Hooks` module,
it cut Array and RSpec::Core::Hooks::HookCollection
allocations by 2000 each:

               class_plus                 count
----------------------------------------  -----
String                                    28000
Array                                     13000
Proc                                       9000
RubyVM::Env                                9000
Hash                                       9000
Array<String>                              5000
RSpec::Core::Hooks::HookCollection         4000
MatchData                                  3000
Array<Module>                              2000
RSpec::Core::Example::ExecutionResult      2000
Module                                     2000
Array<String,Fixnum>                       2000
RSpec::Core::Hooks::HookCollections        1000
RSpec::Core::Example                       1000
Array<RSpec::Core::Example>                1000
RSpec::Core::Metadata::ExampleHash         1000
RSpec::Core::Hooks::AroundHookCollection   1000
RSpec::Core::Metadata::ExampleGroupHash    1000
Class                                      1000
Array<Hash>                                1000

....

Later, our allocations were:

              class_plus                 count
---------------------------------------  -----
String                                   26000
Hash                                     19000
Array                                    18000
Set                                      10000
Proc                                      9000
RubyVM::Env                               9000
RSpec::Core::Hooks::HookCollection        5000
RSpec::Core::FilterableItemRepository     5000
Array<String>                             5000
MatchData                                 3000
RSpec::Core::Example::ExecutionResult     2000
Array<String,Fixnum>                      2000
Module                                    2000
Array<Module>                             2000
RSpec::Core::Metadata::ExampleGroupHash   1000
Class                                     1000
RSpec::Core::Metadata::ExampleHash        1000
RSpec::Core::Example                      1000
Array<RSpec::Core::Example>               1000
Array<Hash>                               1000
RSpec::Core::Hooks::HookCollections       1000


After changing the hooks implementation to lazily
instantiate `HookCollection` instances, it dropped
our allocations by:
  - 8K hashes
  - 10K arrays
  - 10K sets
  - 5K FilterableItemRepository
  - 5K HookCollecion

              class_plus                 count
---------------------------------------  -----
String                                   26000
Hash                                     11000
Array                                     8000
Proc                                      5000
RubyVM::Env                               5000
Array<String>                             5000
MatchData                                 3000
Array<Module>                             2000
Array<String,Fixnum>                      2000
RSpec::Core::Example::ExecutionResult     2000
Module                                    2000
Array<Hash>                               1000
RSpec::Core::Metadata::ExampleGroupHash   1000
Class                                     1000
RSpec::Core::Metadata::ExampleHash        1000
RSpec::Core::Example                      1000
Array<RSpec::Core::Example>               1000
RSpec::Core::Hooks::HookCollections       1000