19 files changed, 652 insertions, 405 deletions

diff --git a/spec/ruby/core/array/fixtures/classes.rb b/spec/ruby/core/array/fixtures/classes.rb
index 8596245fb8..05283c0f74 100644
--- a/spec/ruby/core/array/fixtures/classes.rb
+++ b/spec/ruby/core/array/fixtures/classes.rb
@@ -56,23 +56,20 @@ module ArraySpecs
     101.621, 102.816, 104.010, 105.202, 106.393, 107.583, 108.771, 109.958, 111.144, 112.329,
     113.512, 114.695, 115.876, 117.057, 118.236, 119.414, 120.591, 121.767, 122.942, 124.116,
     125.289, 126.462, 127.633, 128.803, 129.973, 131.141, 132.309, 133.476, 134.642, 135.807,
-      ]
+  ]
 
   def self.measure_sample_fairness(size, samples, iters)
     ary = Array.new(size) { |x| x }
+    expected = iters.fdiv size
     (samples).times do |i|
       chi_results = []
       3.times do
-        counts = Array.new(size) { 0 }
-        expected = iters / size
+        counts = Array.new(size, 0)
         iters.times do
           x = ary.sample(samples)[i]
           counts[x] += 1
         end
-        chi_squared = 0.0
-        counts.each do |count|
-          chi_squared += (((count - expected) ** 2) * 1.0 / expected)
-        end
+        chi_squared = counts.sum {|count| (count - expected) ** 2} / expected
         chi_results << chi_squared
         break if chi_squared <= CHI_SQUARED_CRITICAL_VALUES[size]
       end
@@ -83,17 +80,14 @@ module ArraySpecs
 
   def self.measure_sample_fairness_large_sample_size(size, samples, iters)
     ary = Array.new(size) { |x| x }
-    counts = Array.new(size) { 0 }
-    expected = iters * samples / size
+    counts = Array.new(size, 0)
+    expected = (iters * samples).fdiv size
     iters.times do
       ary.sample(samples).each do |sample|
         counts[sample] += 1
       end
     end
-    chi_squared = 0.0
-    counts.each do |count|
-      chi_squared += (((count - expected) ** 2) * 1.0 / expected)
-    end
+    chi_squared = counts.sum {|count| (count - expected) ** 2} / expected
 
     # Chi squared critical values for tests with 4 degrees of freedom
     # Values obtained from NIST Engineering Statistic Handbook at
@@ -223,366 +217,370 @@ module ArraySpecs
     obj
   end
 
-  LargeArray = ["test_create_table_with_force_true_does_not_drop_nonexisting_table",
- "test_add_table",
- "assert_difference",
- "assert_operator",
- "instance_variables",
- "class",
- "instance_variable_get",
- "__class__",
- "expects",
- "assert_no_difference",
- "name",
- "assert_blank",
- "assert_not_same",
- "is_a?",
- "test_add_table_with_decimals",
- "test_create_table_with_timestamps_should_create_datetime_columns",
- "assert_present",
- "assert_no_match",
- "__instance_of__",
- "assert_deprecated",
- "assert",
- "assert_throws",
- "kind_of?",
- "try",
- "__instance_variable_get__",
- "object_id",
- "timeout",
- "instance_variable_set",
- "assert_nothing_thrown",
- "__instance_variable_set__",
- "copy_object",
- "test_create_table_with_timestamps_should_create_datetime_columns_with_options",
- "assert_not_deprecated",
- "assert_in_delta",
- "id",
- "copy_metaclass",
- "test_create_table_without_a_block",
- "dup",
- "assert_not_nil",
- "send",
- "__instance_variables__",
- "to_sql",
- "mock",
- "assert_send",
- "instance_variable_defined?",
- "clone",
- "require",
- "test_migrator",
- "__instance_variable_defined_eh__",
- "frozen?",
- "test_add_column_not_null_with_default",
- "freeze",
- "test_migrator_one_up",
- "test_migrator_one_down",
- "singleton_methods",
- "method_exists?",
- "create_fixtures",
- "test_migrator_one_up_one_down",
- "test_native_decimal_insert_manual_vs_automatic",
- "instance_exec",
- "__is_a__",
- "test_migrator_double_up",
- "stub",
- "private_methods",
- "stubs",
- "test_migrator_double_down",
- "fixture_path",
- "private_singleton_methods",
- "stub_everything",
- "test_migrator_one_up_with_exception_and_rollback",
- "sequence",
- "protected_methods",
- "enum_for",
- "test_finds_migrations",
- "run_before_mocha",
- "states",
- "protected_singleton_methods",
- "to_json",
- "instance_values",
- "==",
- "mocha_setup",
- "public_methods",
- "test_finds_pending_migrations",
- "mocha_verify",
- "assert_kind_of",
- "===",
- "=~",
- "test_relative_migrations",
- "mocha_teardown",
- "gem",
- "mocha",
- "test_only_loads_pending_migrations",
- "test_add_column_with_precision_and_scale",
- "require_or_load",
- "eql?",
- "require_dependency",
- "test_native_types",
- "test_target_version_zero_should_run_only_once",
- "extend",
- "to_matcher",
- "unloadable",
- "require_association",
- "hash",
- "__id__",
- "load_dependency",
- "equals",
- "test_migrator_db_has_no_schema_migrations_table",
- "test_migrator_verbosity",
- "kind_of",
- "to_yaml",
- "to_bool",
- "test_migrator_verbosity_off",
- "taint",
- "test_migrator_going_down_due_to_version_target",
- "tainted?",
- "mocha_inspect",
- "test_migrator_rollback",
- "vim",
- "untaint",
- "taguri=",
- "test_migrator_forward",
- "test_schema_migrations_table_name",
- "test_proper_table_name",
- "all_of",
- "test_add_drop_table_with_prefix_and_suffix",
- "_setup_callbacks",
- "setup",
- "Not",
- "test_create_table_with_binary_column",
- "assert_not_equal",
- "enable_warnings",
- "acts_like?",
- "Rational",
- "_removed_setup_callbacks",
- "Table",
- "bind",
- "any_of",
- "__method__",
- "test_migrator_with_duplicates",
- "_teardown_callbacks",
- "method",
- "test_migrator_with_duplicate_names",
- "_removed_teardown_callbacks",
- "any_parameters",
- "test_migrator_with_missing_version_numbers",
- "test_add_remove_single_field_using_string_arguments",
- "test_create_table_with_custom_sequence_name",
- "test_add_remove_single_field_using_symbol_arguments",
- "_one_time_conditions_valid_14?",
- "_one_time_conditions_valid_16?",
- "run_callbacks",
- "anything",
- "silence_warnings",
- "instance_variable_names",
- "_fixture_path",
- "copy_instance_variables_from",
- "fixture_path?",
- "has_entry",
- "__marshal__",
- "_fixture_table_names",
- "__kind_of__",
- "fixture_table_names?",
- "test_add_rename",
- "assert_equal",
- "_fixture_class_names",
- "fixture_class_names?",
- "has_entries",
- "_use_transactional_fixtures",
- "people",
- "test_rename_column_using_symbol_arguments",
- "use_transactional_fixtures?",
- "instance_eval",
- "blank?",
- "with_warnings",
- "__nil__",
- "load",
- "metaclass",
- "_use_instantiated_fixtures",
- "has_key",
- "class_eval",
- "present?",
- "test_rename_column",
- "teardown",
- "use_instantiated_fixtures?",
- "method_name",
- "silence_stderr",
- "presence",
- "test_rename_column_preserves_default_value_not_null",
- "silence_stream",
- "_pre_loaded_fixtures",
- "__metaclass__",
- "__fixnum__",
- "pre_loaded_fixtures?",
- "has_value",
- "suppress",
- "to_yaml_properties",
- "test_rename_nonexistent_column",
- "test_add_index",
- "includes",
- "find_correlate_in",
- "equality_predicate_sql",
- "assert_nothing_raised",
- "let",
- "not_predicate_sql",
- "test_rename_column_with_sql_reserved_word",
- "singleton_class",
- "test_rename_column_with_an_index",
- "display",
- "taguri",
- "to_yaml_style",
- "test_remove_column_with_index",
- "size",
- "current_adapter?",
- "test_remove_column_with_multi_column_index",
- "respond_to?",
- "test_change_type_of_not_null_column",
- "is_a",
- "to_a",
- "test_rename_table_for_sqlite_should_work_with_reserved_words",
- "require_library_or_gem",
- "setup_fixtures",
- "equal?",
- "teardown_fixtures",
- "nil?",
- "fixture_table_names",
- "fixture_class_names",
- "test_create_table_without_id",
- "use_transactional_fixtures",
- "test_add_column_with_primary_key_attribute",
- "repair_validations",
- "use_instantiated_fixtures",
- "instance_of?",
- "test_create_table_adds_id",
- "test_rename_table",
- "pre_loaded_fixtures",
- "to_enum",
- "test_create_table_with_not_null_column",
- "instance_of",
- "test_change_column_nullability",
- "optionally",
- "test_rename_table_with_an_index",
- "run",
- "test_change_column",
- "default_test",
- "assert_raise",
- "test_create_table_with_defaults",
- "assert_nil",
- "flunk",
- "regexp_matches",
- "duplicable?",
- "reset_mocha",
- "stubba_method",
- "filter_backtrace",
- "test_create_table_with_limits",
- "responds_with",
- "stubba_object",
- "test_change_column_with_nil_default",
- "assert_block",
- "__show__",
- "assert_date_from_db",
- "__respond_to_eh__",
- "run_in_transaction?",
- "inspect",
- "assert_sql",
- "test_change_column_with_new_default",
- "yaml_equivalent",
- "build_message",
- "to_s",
- "test_change_column_default",
- "assert_queries",
- "pending",
- "as_json",
- "assert_no_queries",
- "test_change_column_quotes_column_names",
- "assert_match",
- "test_keeping_default_and_notnull_constraint_on_change",
- "methods",
- "connection_allow_concurrency_setup",
- "connection_allow_concurrency_teardown",
- "test_create_table_with_primary_key_prefix_as_table_name_with_underscore",
- "__send__",
- "make_connection",
- "assert_raises",
- "tap",
- "with_kcode",
- "assert_instance_of",
- "test_create_table_with_primary_key_prefix_as_table_name",
- "assert_respond_to",
- "test_change_column_default_to_null",
- "assert_same",
- "__extend__"]
-
-  LargeTestArraySorted = ["test_add_column_not_null_with_default",
- "test_add_column_with_precision_and_scale",
- "test_add_column_with_primary_key_attribute",
- "test_add_drop_table_with_prefix_and_suffix",
- "test_add_index",
- "test_add_remove_single_field_using_string_arguments",
- "test_add_remove_single_field_using_symbol_arguments",
- "test_add_rename",
- "test_add_table",
- "test_add_table_with_decimals",
- "test_change_column",
- "test_change_column_default",
- "test_change_column_default_to_null",
- "test_change_column_nullability",
- "test_change_column_quotes_column_names",
- "test_change_column_with_new_default",
- "test_change_column_with_nil_default",
- "test_change_type_of_not_null_column",
- "test_create_table_adds_id",
- "test_create_table_with_binary_column",
- "test_create_table_with_custom_sequence_name",
- "test_create_table_with_defaults",
- "test_create_table_with_force_true_does_not_drop_nonexisting_table",
- "test_create_table_with_limits",
- "test_create_table_with_not_null_column",
- "test_create_table_with_primary_key_prefix_as_table_name",
- "test_create_table_with_primary_key_prefix_as_table_name_with_underscore",
- "test_create_table_with_timestamps_should_create_datetime_columns",
- "test_create_table_with_timestamps_should_create_datetime_columns_with_options",
- "test_create_table_without_a_block",
- "test_create_table_without_id",
- "test_finds_migrations",
- "test_finds_pending_migrations",
- "test_keeping_default_and_notnull_constraint_on_change",
- "test_migrator",
- "test_migrator_db_has_no_schema_migrations_table",
- "test_migrator_double_down",
- "test_migrator_double_up",
- "test_migrator_forward",
- "test_migrator_going_down_due_to_version_target",
- "test_migrator_one_down",
- "test_migrator_one_up",
- "test_migrator_one_up_one_down",
- "test_migrator_one_up_with_exception_and_rollback",
- "test_migrator_rollback",
- "test_migrator_verbosity",
- "test_migrator_verbosity_off",
- "test_migrator_with_duplicate_names",
- "test_migrator_with_duplicates",
- "test_migrator_with_missing_version_numbers",
- "test_native_decimal_insert_manual_vs_automatic",
- "test_native_types",
- "test_only_loads_pending_migrations",
- "test_proper_table_name",
- "test_relative_migrations",
- "test_remove_column_with_index",
- "test_remove_column_with_multi_column_index",
- "test_rename_column",
- "test_rename_column_preserves_default_value_not_null",
- "test_rename_column_using_symbol_arguments",
- "test_rename_column_with_an_index",
- "test_rename_column_with_sql_reserved_word",
- "test_rename_nonexistent_column",
- "test_rename_table",
- "test_rename_table_for_sqlite_should_work_with_reserved_words",
- "test_rename_table_with_an_index",
- "test_schema_migrations_table_name",
- "test_target_version_zero_should_run_only_once"]
+  LargeArray = [
+    "test_create_table_with_force_true_does_not_drop_nonexisting_table",
+    "test_add_table",
+    "assert_difference",
+    "assert_operator",
+    "instance_variables",
+    "class",
+    "instance_variable_get",
+    "__class__",
+    "expects",
+    "assert_no_difference",
+    "name",
+    "assert_blank",
+    "assert_not_same",
+    "is_a?",
+    "test_add_table_with_decimals",
+    "test_create_table_with_timestamps_should_create_datetime_columns",
+    "assert_present",
+    "assert_no_match",
+    "__instance_of__",
+    "assert_deprecated",
+    "assert",
+    "assert_throws",
+    "kind_of?",
+    "try",
+    "__instance_variable_get__",
+    "object_id",
+    "timeout",
+    "instance_variable_set",
+    "assert_nothing_thrown",
+    "__instance_variable_set__",
+    "copy_object",
+    "test_create_table_with_timestamps_should_create_datetime_columns_with_options",
+    "assert_not_deprecated",
+    "assert_in_delta",
+    "id",
+    "copy_metaclass",
+    "test_create_table_without_a_block",
+    "dup",
+    "assert_not_nil",
+    "send",
+    "__instance_variables__",
+    "to_sql",
+    "mock",
+    "assert_send",
+    "instance_variable_defined?",
+    "clone",
+    "require",
+    "test_migrator",
+    "__instance_variable_defined_eh__",
+    "frozen?",
+    "test_add_column_not_null_with_default",
+    "freeze",
+    "test_migrator_one_up",
+    "test_migrator_one_down",
+    "singleton_methods",
+    "method_exists?",
+    "create_fixtures",
+    "test_migrator_one_up_one_down",
+    "test_native_decimal_insert_manual_vs_automatic",
+    "instance_exec",
+    "__is_a__",
+    "test_migrator_double_up",
+    "stub",
+    "private_methods",
+    "stubs",
+    "test_migrator_double_down",
+    "fixture_path",
+    "private_singleton_methods",
+    "stub_everything",
+    "test_migrator_one_up_with_exception_and_rollback",
+    "sequence",
+    "protected_methods",
+    "enum_for",
+    "test_finds_migrations",
+    "run_before_mocha",
+    "states",
+    "protected_singleton_methods",
+    "to_json",
+    "instance_values",
+    "==",
+    "mocha_setup",
+    "public_methods",
+    "test_finds_pending_migrations",
+    "mocha_verify",
+    "assert_kind_of",
+    "===",
+    "=~",
+    "test_relative_migrations",
+    "mocha_teardown",
+    "gem",
+    "mocha",
+    "test_only_loads_pending_migrations",
+    "test_add_column_with_precision_and_scale",
+    "require_or_load",
+    "eql?",
+    "require_dependency",
+    "test_native_types",
+    "test_target_version_zero_should_run_only_once",
+    "extend",
+    "to_matcher",
+    "unloadable",
+    "require_association",
+    "hash",
+    "__id__",
+    "load_dependency",
+    "equals",
+    "test_migrator_db_has_no_schema_migrations_table",
+    "test_migrator_verbosity",
+    "kind_of",
+    "to_yaml",
+    "to_bool",
+    "test_migrator_verbosity_off",
+    "taint",
+    "test_migrator_going_down_due_to_version_target",
+    "tainted?",
+    "mocha_inspect",
+    "test_migrator_rollback",
+    "vim",
+    "untaint",
+    "taguri=",
+    "test_migrator_forward",
+    "test_schema_migrations_table_name",
+    "test_proper_table_name",
+    "all_of",
+    "test_add_drop_table_with_prefix_and_suffix",
+    "_setup_callbacks",
+    "setup",
+    "Not",
+    "test_create_table_with_binary_column",
+    "assert_not_equal",
+    "enable_warnings",
+    "acts_like?",
+    "Rational",
+    "_removed_setup_callbacks",
+    "Table",
+    "bind",
+    "any_of",
+    "__method__",
+    "test_migrator_with_duplicates",
+    "_teardown_callbacks",
+    "method",
+    "test_migrator_with_duplicate_names",
+    "_removed_teardown_callbacks",
+    "any_parameters",
+    "test_migrator_with_missing_version_numbers",
+    "test_add_remove_single_field_using_string_arguments",
+    "test_create_table_with_custom_sequence_name",
+    "test_add_remove_single_field_using_symbol_arguments",
+    "_one_time_conditions_valid_14?",
+    "_one_time_conditions_valid_16?",
+    "run_callbacks",
+    "anything",
+    "silence_warnings",
+    "instance_variable_names",
+    "_fixture_path",
+    "copy_instance_variables_from",
+    "fixture_path?",
+    "has_entry",
+    "__marshal__",
+    "_fixture_table_names",
+    "__kind_of__",
+    "fixture_table_names?",
+    "test_add_rename",
+    "assert_equal",
+    "_fixture_class_names",
+    "fixture_class_names?",
+    "has_entries",
+    "_use_transactional_fixtures",
+    "people",
+    "test_rename_column_using_symbol_arguments",
+    "use_transactional_fixtures?",
+    "instance_eval",
+    "blank?",
+    "with_warnings",
+    "__nil__",
+    "load",
+    "metaclass",
+    "_use_instantiated_fixtures",
+    "has_key",
+    "class_eval",
+    "present?",
+    "test_rename_column",
+    "teardown",
+    "use_instantiated_fixtures?",
+    "method_name",
+    "silence_stderr",
+    "presence",
+    "test_rename_column_preserves_default_value_not_null",
+    "silence_stream",
+    "_pre_loaded_fixtures",
+    "__metaclass__",
+    "__fixnum__",
+    "pre_loaded_fixtures?",
+    "has_value",
+    "suppress",
+    "to_yaml_properties",
+    "test_rename_nonexistent_column",
+    "test_add_index",
+    "includes",
+    "find_correlate_in",
+    "equality_predicate_sql",
+    "assert_nothing_raised",
+    "let",
+    "not_predicate_sql",
+    "test_rename_column_with_sql_reserved_word",
+    "singleton_class",
+    "test_rename_column_with_an_index",
+    "display",
+    "taguri",
+    "to_yaml_style",
+    "test_remove_column_with_index",
+    "size",
+    "current_adapter?",
+    "test_remove_column_with_multi_column_index",
+    "respond_to?",
+    "test_change_type_of_not_null_column",
+    "is_a",
+    "to_a",
+    "test_rename_table_for_sqlite_should_work_with_reserved_words",
+    "require_library_or_gem",
+    "setup_fixtures",
+    "equal?",
+    "teardown_fixtures",
+    "nil?",
+    "fixture_table_names",
+    "fixture_class_names",
+    "test_create_table_without_id",
+    "use_transactional_fixtures",
+    "test_add_column_with_primary_key_attribute",
+    "repair_validations",
+    "use_instantiated_fixtures",
+    "instance_of?",
+    "test_create_table_adds_id",
+    "test_rename_table",
+    "pre_loaded_fixtures",
+    "to_enum",
+    "test_create_table_with_not_null_column",
+    "instance_of",
+    "test_change_column_nullability",
+    "optionally",
+    "test_rename_table_with_an_index",
+    "run",
+    "test_change_column",
+    "default_test",
+    "assert_raise",
+    "test_create_table_with_defaults",
+    "assert_nil",
+    "flunk",
+    "regexp_matches",
+    "duplicable?",
+    "reset_mocha",
+    "stubba_method",
+    "filter_backtrace",
+    "test_create_table_with_limits",
+    "responds_with",
+    "stubba_object",
+    "test_change_column_with_nil_default",
+    "assert_block",
+    "__show__",
+    "assert_date_from_db",
+    "__respond_to_eh__",
+    "run_in_transaction?",
+    "inspect",
+    "assert_sql",
+    "test_change_column_with_new_default",
+    "yaml_equivalent",
+    "build_message",
+    "to_s",
+    "test_change_column_default",
+    "assert_queries",
+    "pending",
+    "as_json",
+    "assert_no_queries",
+    "test_change_column_quotes_column_names",
+    "assert_match",
+    "test_keeping_default_and_notnull_constraint_on_change",
+    "methods",
+    "connection_allow_concurrency_setup",
+    "connection_allow_concurrency_teardown",
+    "test_create_table_with_primary_key_prefix_as_table_name_with_underscore",
+    "__send__",
+    "make_connection",
+    "assert_raises",
+    "tap",
+    "with_kcode",
+    "assert_instance_of",
+    "test_create_table_with_primary_key_prefix_as_table_name",
+    "assert_respond_to",
+    "test_change_column_default_to_null",
+    "assert_same",
+    "__extend__",
+  ]
+
+  LargeTestArraySorted = [
+    "test_add_column_not_null_with_default",
+    "test_add_column_with_precision_and_scale",
+    "test_add_column_with_primary_key_attribute",
+    "test_add_drop_table_with_prefix_and_suffix",
+    "test_add_index",
+    "test_add_remove_single_field_using_string_arguments",
+    "test_add_remove_single_field_using_symbol_arguments",
+    "test_add_rename",
+    "test_add_table",
+    "test_add_table_with_decimals",
+    "test_change_column",
+    "test_change_column_default",
+    "test_change_column_default_to_null",
+    "test_change_column_nullability",
+    "test_change_column_quotes_column_names",
+    "test_change_column_with_new_default",
+    "test_change_column_with_nil_default",
+    "test_change_type_of_not_null_column",
+    "test_create_table_adds_id",
+    "test_create_table_with_binary_column",
+    "test_create_table_with_custom_sequence_name",
+    "test_create_table_with_defaults",
+    "test_create_table_with_force_true_does_not_drop_nonexisting_table",
+    "test_create_table_with_limits",
+    "test_create_table_with_not_null_column",
+    "test_create_table_with_primary_key_prefix_as_table_name",
+    "test_create_table_with_primary_key_prefix_as_table_name_with_underscore",
+    "test_create_table_with_timestamps_should_create_datetime_columns",
+    "test_create_table_with_timestamps_should_create_datetime_columns_with_options",
+    "test_create_table_without_a_block",
+    "test_create_table_without_id",
+    "test_finds_migrations",
+    "test_finds_pending_migrations",
+    "test_keeping_default_and_notnull_constraint_on_change",
+    "test_migrator",
+    "test_migrator_db_has_no_schema_migrations_table",
+    "test_migrator_double_down",
+    "test_migrator_double_up",
+    "test_migrator_forward",
+    "test_migrator_going_down_due_to_version_target",
+    "test_migrator_one_down",
+    "test_migrator_one_up",
+    "test_migrator_one_up_one_down",
+    "test_migrator_one_up_with_exception_and_rollback",
+    "test_migrator_rollback",
+    "test_migrator_verbosity",
+    "test_migrator_verbosity_off",
+    "test_migrator_with_duplicate_names",
+    "test_migrator_with_duplicates",
+    "test_migrator_with_missing_version_numbers",
+    "test_native_decimal_insert_manual_vs_automatic",
+    "test_native_types",
+    "test_only_loads_pending_migrations",
+    "test_proper_table_name",
+    "test_relative_migrations",
+    "test_remove_column_with_index",
+    "test_remove_column_with_multi_column_index",
+    "test_rename_column",
+    "test_rename_column_preserves_default_value_not_null",
+    "test_rename_column_using_symbol_arguments",
+    "test_rename_column_with_an_index",
+    "test_rename_column_with_sql_reserved_word",
+    "test_rename_nonexistent_column",
+    "test_rename_table",
+    "test_rename_table_for_sqlite_should_work_with_reserved_words",
+    "test_rename_table_with_an_index",
+    "test_schema_migrations_table_name",
+    "test_target_version_zero_should_run_only_once",
+  ]
 
   class PrivateToAry
     private
diff --git a/spec/ruby/core/array/pack/buffer_spec.rb b/spec/ruby/core/array/pack/buffer_spec.rb
index f1206efb3e..b77b2d1efa 100644
--- a/spec/ruby/core/array/pack/buffer_spec.rb
+++ b/spec/ruby/core/array/pack/buffer_spec.rb
@@ -28,6 +28,16 @@ describe "Array#pack with :buffer option" do
       TypeError, "buffer must be String, not Array")
   end
 
+  it "raise FrozenError if buffer is frozen" do
+    -> { [65].pack("c", buffer: "frozen-string".freeze) }.should raise_error(FrozenError)
+  end
+
+  it "preserves the encoding of the given buffer" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    [65, 66, 67].pack("ccc", buffer: buffer)
+    buffer.encoding.should == Encoding::ISO_8859_1
+  end
+
   context "offset (@) is specified" do
     it 'keeps buffer content if it is longer than offset' do
       n = [ 65, 66, 67 ]
diff --git a/spec/ruby/core/binding/dup_spec.rb b/spec/ruby/core/binding/dup_spec.rb
index 55fac6e333..4eff66bd9a 100644
--- a/spec/ruby/core/binding/dup_spec.rb
+++ b/spec/ruby/core/binding/dup_spec.rb
@@ -10,4 +10,21 @@ describe "Binding#dup" do
     bind.frozen?.should == true
     bind.dup.frozen?.should == false
   end
+
+  it "retains original binding variables but the list is distinct" do
+    bind1 = binding
+    eval "a = 1", bind1
+
+    bind2 = bind1.dup
+    eval("a = 2", bind2)
+    eval("a", bind1).should == 2
+    eval("a", bind2).should == 2
+
+    eval("b = 2", bind2)
+    -> { eval("b", bind1) }.should raise_error(NameError)
+    eval("b", bind2).should == 2
+
+    bind1.local_variables.sort.should == [:a, :bind1, :bind2]
+    bind2.local_variables.sort.should == [:a, :b, :bind1, :bind2]
+  end
 end
diff --git a/spec/ruby/core/binding/irb_spec.rb b/spec/ruby/core/binding/irb_spec.rb
index 25521f0dd7..2607c7ef33 100644
--- a/spec/ruby/core/binding/irb_spec.rb
+++ b/spec/ruby/core/binding/irb_spec.rb
@@ -10,7 +10,7 @@ describe "Binding#irb" do
       IO.popen([envs, *ruby_exe, irb_fixture, chdir: dir], "r+") do |pipe|
         pipe.puts "a ** 2"
         pipe.puts "exit"
-        pipe.readlines.map(&:chomp)
+        pipe.readlines.map(&:chomp).reject(&:empty?)
       end
     end
 
diff --git a/spec/ruby/core/enumerator/next_values_spec.rb b/spec/ruby/core/enumerator/next_values_spec.rb
index 201b5d323f..2202700c58 100644
--- a/spec/ruby/core/enumerator/next_values_spec.rb
+++ b/spec/ruby/core/enumerator/next_values_spec.rb
@@ -11,6 +11,7 @@ describe "Enumerator#next_values" do
       yield :e1, :e2, :e3
       yield nil
       yield
+      yield [:f1, :f2]
     end
 
     @e = o.to_enum
@@ -48,8 +49,13 @@ describe "Enumerator#next_values" do
     @e.next_values.should == []
   end
 
-  it "raises StopIteration if called on a finished enumerator" do
+  it "returns an array of array if yield is called with an array" do
     7.times { @e.next }
+    @e.next_values.should == [[:f1, :f2]]
+  end
+
+  it "raises StopIteration if called on a finished enumerator" do
+    8.times { @e.next }
     -> { @e.next_values }.should raise_error(StopIteration)
   end
 end
diff --git a/spec/ruby/core/enumerator/peek_values_spec.rb b/spec/ruby/core/enumerator/peek_values_spec.rb
index 7865546515..8b84fc8afc 100644
--- a/spec/ruby/core/enumerator/peek_values_spec.rb
+++ b/spec/ruby/core/enumerator/peek_values_spec.rb
@@ -11,6 +11,7 @@ describe "Enumerator#peek_values" do
       yield :e1, :e2, :e3
       yield nil
       yield
+      yield [:f1, :f2]
     end
 
     @e = o.to_enum
@@ -50,8 +51,13 @@ describe "Enumerator#peek_values" do
     @e.peek_values.should == []
   end
 
-  it "raises StopIteration if called on a finished enumerator" do
+  it "returns an array of array if yield is called with an array" do
     7.times { @e.next }
+    @e.peek_values.should == [[:f1, :f2]]
+  end
+
+  it "raises StopIteration if called on a finished enumerator" do
+    8.times { @e.next }
     -> { @e.peek_values }.should raise_error(StopIteration)
   end
 end
diff --git a/spec/ruby/core/io/pread_spec.rb b/spec/ruby/core/io/pread_spec.rb
index 28afc80e5c..6d93b432c2 100644
--- a/spec/ruby/core/io/pread_spec.rb
+++ b/spec/ruby/core/io/pread_spec.rb
@@ -22,7 +22,7 @@ guard -> { platform_is_not :windows or ruby_version_is "3.3" } do
 
     it "accepts a length, an offset, and an output buffer" do
       buffer = +"foo"
-      @file.pread(3, 4, buffer)
+      @file.pread(3, 4, buffer).should.equal?(buffer)
       buffer.should == "567"
     end
 
@@ -38,6 +38,13 @@ guard -> { platform_is_not :windows or ruby_version_is "3.3" } do
       buffer.should == "12345"
     end
 
+    it "preserves the encoding of the given buffer" do
+      buffer = ''.encode(Encoding::ISO_8859_1)
+      @file.pread(10, 0, buffer)
+
+      buffer.encoding.should == Encoding::ISO_8859_1
+    end
+
     it "does not advance the file pointer" do
       @file.pread(4, 0).should == "1234"
       @file.read.should == "1234567890"
diff --git a/spec/ruby/core/io/read_spec.rb b/spec/ruby/core/io/read_spec.rb
index eb3652e692..8741d9f017 100644
--- a/spec/ruby/core/io/read_spec.rb
+++ b/spec/ruby/core/io/read_spec.rb
@@ -376,6 +376,21 @@ describe "IO#read" do
     buf.should == @contents[0..4]
   end
 
+  it "preserves the encoding of the given buffer" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    @io.read(10, buffer)
+
+    buffer.encoding.should == Encoding::ISO_8859_1
+  end
+
+  # https://bugs.ruby-lang.org/issues/20416
+  it "does not preserve the encoding of the given buffer when max length is not provided" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    @io.read(nil, buffer)
+
+    buffer.encoding.should_not == Encoding::ISO_8859_1
+  end
+
   it "returns the given buffer" do
     buf = +""
 
diff --git a/spec/ruby/core/io/readpartial_spec.rb b/spec/ruby/core/io/readpartial_spec.rb
index 0060beb545..0852f20b2d 100644
--- a/spec/ruby/core/io/readpartial_spec.rb
+++ b/spec/ruby/core/io/readpartial_spec.rb
@@ -62,7 +62,7 @@ describe "IO#readpartial" do
     buffer = +"existing content"
     @wr.write("hello world")
     @wr.close
-    @rd.readpartial(11, buffer)
+    @rd.readpartial(11, buffer).should.equal?(buffer)
     buffer.should == "hello world"
   end
 
@@ -106,6 +106,7 @@ describe "IO#readpartial" do
     @wr.write("abc")
     @wr.close
     @rd.readpartial(10, buffer)
+
     buffer.encoding.should == Encoding::ISO_8859_1
   end
 end
diff --git a/spec/ruby/core/io/sysread_spec.rb b/spec/ruby/core/io/sysread_spec.rb
index 003bb9eb94..8851214283 100644
--- a/spec/ruby/core/io/sysread_spec.rb
+++ b/spec/ruby/core/io/sysread_spec.rb
@@ -97,7 +97,7 @@ describe "IO#sysread on a file" do
 
   it "discards the existing buffer content upon successful read" do
     buffer = +"existing content"
-    @file.sysread(11, buffer)
+    @file.sysread(11, buffer).should.equal?(buffer)
     buffer.should == "01234567890"
   end
 
@@ -107,6 +107,13 @@ describe "IO#sysread on a file" do
     -> { @file.sysread(1, buffer) }.should raise_error(EOFError)
     buffer.should be_empty
   end
+
+  it "preserves the encoding of the given buffer" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    string = @file.sysread(10, buffer)
+
+    buffer.encoding.should == Encoding::ISO_8859_1
+  end
 end
 
 describe "IO#sysread" do
diff --git a/spec/ruby/core/module/include_spec.rb b/spec/ruby/core/module/include_spec.rb
index c073bc31ca..78f6b41031 100644
--- a/spec/ruby/core/module/include_spec.rb
+++ b/spec/ruby/core/module/include_spec.rb
@@ -47,6 +47,34 @@ describe "Module#include" do
     -> { ModuleSpecs::SubclassSpec.include(ModuleSpecs::Subclass.new) }.should_not raise_error(TypeError)
   end
 
+  ruby_version_is ""..."3.2" do
+    it "raises ArgumentError when the argument is a refinement" do
+      refinement = nil
+
+      Module.new do
+        refine String do
+          refinement = self
+        end
+      end
+
+      -> { ModuleSpecs::Basic.include(refinement) }.should raise_error(ArgumentError, "refinement module is not allowed")
+    end
+  end
+
+  ruby_version_is "3.2" do
+    it "raises a TypeError when the argument is a refinement" do
+      refinement = nil
+
+      Module.new do
+        refine String do
+          refinement = self
+        end
+      end
+
+      -> { ModuleSpecs::Basic.include(refinement) }.should raise_error(TypeError, "Cannot include refinement")
+    end
+  end
+
   it "imports constants to modules and classes" do
     ModuleSpecs::A.constants.should include(:CONSTANT_A)
     ModuleSpecs::B.constants.should include(:CONSTANT_A, :CONSTANT_B)
diff --git a/spec/ruby/core/module/prepend_spec.rb b/spec/ruby/core/module/prepend_spec.rb
index c90fa9700e..b40d12f0de 100644
--- a/spec/ruby/core/module/prepend_spec.rb
+++ b/spec/ruby/core/module/prepend_spec.rb
@@ -75,6 +75,26 @@ describe "Module#prepend" do
     foo.call.should == 'm'
   end
 
+  it "updates the optimized method when a prepended module is updated" do
+    out = ruby_exe(<<~RUBY)
+    module M; end
+    class Integer
+      prepend M
+    end
+    l = -> { 1 + 2 }
+    p l.call
+    M.module_eval do
+      def +(o)
+        $called = true
+        super(o)
+      end
+    end
+    p l.call
+    p $called
+    RUBY
+    out.should == "3\n3\ntrue\n"
+  end
+
   it "updates the method when there is a base included method and the prepended module overrides it" do
     base_module = Module.new do
       def foo
@@ -415,6 +435,34 @@ describe "Module#prepend" do
     -> { ModuleSpecs::SubclassSpec.prepend(ModuleSpecs::Subclass.new) }.should_not raise_error(TypeError)
   end
 
+  ruby_version_is ""..."3.2" do
+    it "raises ArgumentError when the argument is a refinement" do
+      refinement = nil
+
+      Module.new do
+        refine String do
+          refinement = self
+        end
+      end
+
+      -> { ModuleSpecs::Basic.prepend(refinement) }.should raise_error(ArgumentError, "refinement module is not allowed")
+    end
+  end
+
+  ruby_version_is "3.2" do
+    it "raises a TypeError when the argument is a refinement" do
+      refinement = nil
+
+      Module.new do
+        refine String do
+          refinement = self
+        end
+      end
+
+      -> { ModuleSpecs::Basic.prepend(refinement) }.should raise_error(TypeError, "Cannot prepend refinement")
+    end
+  end
+
   it "imports constants" do
     m1 = Module.new
     m1::MY_CONSTANT = 1
diff --git a/spec/ruby/core/string/chilled_string_spec.rb b/spec/ruby/core/string/chilled_string_spec.rb
index 8de4fc421b..9f81b1af6d 100644
--- a/spec/ruby/core/string/chilled_string_spec.rb
+++ b/spec/ruby/core/string/chilled_string_spec.rb
@@ -3,8 +3,8 @@ require_relative '../../spec_helper'
 describe "chilled String" do
   guard -> { ruby_version_is "3.4" and !"test".equal?("test") } do
     describe "#frozen?" do
-      it "returns true" do
-        "chilled".frozen?.should == true
+      it "returns false" do
+        "chilled".frozen?.should == false
       end
     end
 
@@ -45,7 +45,7 @@ describe "chilled String" do
         input.should == "chilled-mutated"
       end
 
-      it "emits a warning on singleton_class creaation" do
+      it "emits a warning on singleton_class creation" do
         -> {
           "chilled".singleton_class
         }.should complain(/literal string will be frozen in the future/)
@@ -57,12 +57,14 @@ describe "chilled String" do
         }.should complain(/literal string will be frozen in the future/)
       end
 
-      it "raises FrozenError after the string was explictly frozen" do
+      it "raises FrozenError after the string was explicitly frozen" do
         input = "chilled"
         input.freeze
         -> {
+          -> {
           input << "mutated"
-        }.should raise_error(FrozenError)
+          }.should raise_error(FrozenError)
+        }.should_not complain(/literal string will be frozen in the future/)
       end
     end
   end
diff --git a/spec/ruby/core/string/index_spec.rb b/spec/ruby/core/string/index_spec.rb
index be79708045..835263a2cd 100644
--- a/spec/ruby/core/string/index_spec.rb
+++ b/spec/ruby/core/string/index_spec.rb
@@ -231,6 +231,17 @@ describe "String#index with Regexp" do
     $~.should == nil
   end
 
+  ruby_bug "#20421", ""..."3.3" do
+    it "always clear $~" do
+      "a".index(/a/)
+      $~.should_not == nil
+
+      string = "blablabla"
+      string.index(/bla/, string.length + 1)
+      $~.should == nil
+    end
+  end
+
   it "starts the search at the given offset" do
     "blablabla".index(/.{0}/, 5).should == 5
     "blablabla".index(/.{1}/, 5).should == 5
diff --git a/spec/ruby/core/string/modulo_spec.rb b/spec/ruby/core/string/modulo_spec.rb
index bf96a82874..9045afa263 100644
--- a/spec/ruby/core/string/modulo_spec.rb
+++ b/spec/ruby/core/string/modulo_spec.rb
@@ -55,33 +55,48 @@ describe "String#%" do
     -> { ("foo%" % [])}.should raise_error(ArgumentError)
   end
 
-  it "formats single % character before a newline as literal %" do
-    ("%\n" % []).should == "%\n"
-    ("foo%\n" % []).should == "foo%\n"
-    ("%\n.3f" % 1.2).should == "%\n.3f"
-  end
+  ruby_version_is ""..."3.4" do
+    it "formats single % character before a newline as literal %" do
+      ("%\n" % []).should == "%\n"
+      ("foo%\n" % []).should == "foo%\n"
+      ("%\n.3f" % 1.2).should == "%\n.3f"
+    end
 
-  it "formats single % character before a NUL as literal %" do
-    ("%\0" % []).should == "%\0"
-    ("foo%\0" % []).should == "foo%\0"
-    ("%\0.3f" % 1.2).should == "%\0.3f"
-  end
+    it "formats single % character before a NUL as literal %" do
+      ("%\0" % []).should == "%\0"
+      ("foo%\0" % []).should == "foo%\0"
+      ("%\0.3f" % 1.2).should == "%\0.3f"
+    end
 
-  it "raises an error if single % appears anywhere else" do
-    -> { (" % " % []) }.should raise_error(ArgumentError)
-    -> { ("foo%quux" % []) }.should raise_error(ArgumentError)
-  end
+    it "raises an error if single % appears anywhere else" do
+      -> { (" % " % []) }.should raise_error(ArgumentError)
+      -> { ("foo%quux" % []) }.should raise_error(ArgumentError)
+    end
 
-  it "raises an error if NULL or \\n appear anywhere else in the format string" do
-    begin
-      old_debug, $DEBUG = $DEBUG, false
+    it "raises an error if NULL or \\n appear anywhere else in the format string" do
+      begin
+        old_debug, $DEBUG = $DEBUG, false
 
+        -> { "%.\n3f" % 1.2 }.should raise_error(ArgumentError)
+        -> { "%.3\nf" % 1.2 }.should raise_error(ArgumentError)
+        -> { "%.\03f" % 1.2 }.should raise_error(ArgumentError)
+        -> { "%.3\0f" % 1.2 }.should raise_error(ArgumentError)
+      ensure
+        $DEBUG = old_debug
+      end
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "raises an ArgumentError if % is not followed by a conversion specifier" do
+      -> { "%" % [] }.should raise_error(ArgumentError)
+      -> { "%\n" % [] }.should raise_error(ArgumentError)
+      -> { "%\0" % [] }.should raise_error(ArgumentError)
+      -> { " % " % [] }.should raise_error(ArgumentError)
       -> { "%.\n3f" % 1.2 }.should raise_error(ArgumentError)
       -> { "%.3\nf" % 1.2 }.should raise_error(ArgumentError)
       -> { "%.\03f" % 1.2 }.should raise_error(ArgumentError)
       -> { "%.3\0f" % 1.2 }.should raise_error(ArgumentError)
-    ensure
-      $DEBUG = old_debug
     end
   end
 
@@ -125,8 +140,16 @@ describe "String#%" do
     end
   end
 
-  it "replaces trailing absolute argument specifier without type with percent sign" do
-    ("hello %1$" % "foo").should == "hello %"
+  ruby_version_is ""..."3.4" do
+    it "replaces trailing absolute argument specifier without type with percent sign" do
+      ("hello %1$" % "foo").should == "hello %"
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "raises an ArgumentError if absolute argument specifier is followed by a conversion specifier" do
+      -> { "hello %1$" % "foo" }.should raise_error(ArgumentError)
+    end
   end
 
   it "raises an ArgumentError when given invalid argument specifiers" do
diff --git a/spec/ruby/core/tracepoint/inspect_spec.rb b/spec/ruby/core/tracepoint/inspect_spec.rb
index cc6bf0f842..0c94a94d5c 100644
--- a/spec/ruby/core/tracepoint/inspect_spec.rb
+++ b/spec/ruby/core/tracepoint/inspect_spec.rb
@@ -24,6 +24,8 @@ describe 'TracePoint#inspect' do
     line = nil
     TracePoint.new(:line) { |tp|
       next unless TracePointSpec.target_thread?
+      next unless tp.path == __FILE__
+
       inspect ||= tp.inspect
     }.enable do
       line = __LINE__
@@ -37,6 +39,8 @@ describe 'TracePoint#inspect' do
     line = nil
     TracePoint.new(:call) { |tp|
       next unless TracePointSpec.target_thread?
+      next unless tp.path == __FILE__
+
       inspect ||= tp.inspect
     }.enable do
       line = __LINE__ + 1
@@ -52,6 +56,8 @@ describe 'TracePoint#inspect' do
     line = nil
     TracePoint.new(:return) { |tp|
       next unless TracePointSpec.target_thread?
+      next unless tp.path == __FILE__
+
       inspect ||= tp.inspect
     }.enable do
       line = __LINE__ + 4
@@ -69,6 +75,8 @@ describe 'TracePoint#inspect' do
     inspect = nil
     tracepoint = TracePoint.new(:c_call) { |tp|
       next unless TracePointSpec.target_thread?
+      next unless tp.path == __FILE__
+
       inspect ||= tp.inspect
     }
     line = __LINE__ + 2
@@ -84,6 +92,8 @@ describe 'TracePoint#inspect' do
     line = nil
     TracePoint.new(:class) { |tp|
       next unless TracePointSpec.target_thread?
+      next unless tp.path == __FILE__
+
       inspect ||= tp.inspect
     }.enable do
       line = __LINE__ + 1
@@ -100,6 +110,7 @@ describe 'TracePoint#inspect' do
     thread_inspection = nil
     TracePoint.new(:thread_begin) { |tp|
       next unless Thread.current == thread
+
       inspect ||= tp.inspect
     }.enable(target_thread: nil) do
       thread = Thread.new {}
@@ -116,6 +127,7 @@ describe 'TracePoint#inspect' do
     thread_inspection = nil
     TracePoint.new(:thread_end) { |tp|
       next unless Thread.current == thread
+
       inspect ||= tp.inspect
     }.enable(target_thread: nil) do
       thread = Thread.new {}
diff --git a/spec/ruby/core/warning/element_reference_spec.rb b/spec/ruby/core/warning/element_reference_spec.rb
index 8cb4018c20..c0ed37ef13 100644
--- a/spec/ruby/core/warning/element_reference_spec.rb
+++ b/spec/ruby/core/warning/element_reference_spec.rb
@@ -2,6 +2,10 @@ require_relative '../../spec_helper'
 
 describe "Warning.[]" do
   it "returns default values for categories :deprecated and :experimental" do
+    # If any warning options were set on the Ruby that will be executed, then
+    # it's possible this test will fail. In this case we will skip this test.
+    skip if ruby_exe.any? { |opt| opt.start_with?("-W") }
+
     ruby_exe('p [Warning[:deprecated], Warning[:experimental]]').chomp.should == "[false, true]"
     ruby_exe('p [Warning[:deprecated], Warning[:experimental]]', options: "-w").chomp.should == "[true, true]"
   end
diff --git a/spec/ruby/core/warning/performance_warning_spec.rb b/spec/ruby/core/warning/performance_warning_spec.rb
new file mode 100644
index 0000000000..ab0badcd3d
--- /dev/null
+++ b/spec/ruby/core/warning/performance_warning_spec.rb
@@ -0,0 +1,28 @@
+require_relative '../../spec_helper'
+
+
+describe "Performance warnings" do
+  guard -> { ruby_version_is("3.4") || RUBY_ENGINE == "truffleruby" } do
+    # Optimising Integer, Float or Symbol methods is kind of implementation detail
+    # but multiple implementations do so. So it seems reasonable to have a test case
+    # for at least one such common method.
+    # See https://bugs.ruby-lang.org/issues/20429
+    context "when redefined optimised methods" do
+      it "emits performance warning for redefining Integer#+" do
+        code = <<~CODE
+          Warning[:performance] = true
+
+          class Integer
+            ORIG_METHOD = instance_method(:+)
+
+            def +(...)
+              ORIG_METHOD.bind(self).call(...)
+            end
+          end
+        CODE
+
+        ruby_exe(code, args: "2>&1").should.include?("warning: Redefining 'Integer#+' disables interpreter and JIT optimizations")
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/warning/warn_spec.rb b/spec/ruby/core/warning/warn_spec.rb
index 8f96fe9287..1c21fe29e0 100644
--- a/spec/ruby/core/warning/warn_spec.rb
+++ b/spec/ruby/core/warning/warn_spec.rb
@@ -121,6 +121,30 @@ describe "Warning.warn" do
     end
   end
 
+  ruby_bug '#19530', ''...'3.4' do
+    it "isn't called by Kernel.warn when category is :deprecated but Warning[:deprecated] is false" do
+      warn_deprecated = Warning[:deprecated]
+      begin
+        Warning[:deprecated] = false
+        Warning.should_not_receive(:warn)
+        Kernel.warn("foo", category: :deprecated)
+      ensure
+        Warning[:deprecated] = warn_deprecated
+      end
+    end
+
+    it "isn't called by Kernel.warn when category is :experimental but Warning[:experimental] is false" do
+      warn_experimental = Warning[:experimental]
+      begin
+        Warning[:experimental] = false
+        Warning.should_not_receive(:warn)
+        Kernel.warn("foo", category: :experimental)
+      ensure
+        Warning[:experimental] = warn_experimental
+      end
+    end
+  end
+
   it "prints the message when VERBOSE is false" do
     -> { Warning.warn("foo") }.should complain("foo")
   end