Required files
active_support
active_support
active_record/base
active_record/named_scope
active_record/observer
active_record/query_cache
active_record/validations
active_record/callbacks
active_record/reflection
active_record/associations
active_record/association_preload
active_record/aggregations
active_record/transactions
active_record/timestamp
active_record/locking/optimistic
active_record/locking/pessimistic
active_record/migration
active_record/schema
active_record/calculations
active_record/serialization
active_record/attribute_methods
active_record/dirty
active_record/dynamic_finder_match
active_record/connection_adapters/abstract_adapter
active_record/schema_dumper
active_record/i18n_interpolation_deprecation