Don't use this:

    scope :red, where(color: 'red')
    default_scope where(color: 'red')

Use this:

    scope :red, -> { where(color: 'red') }
    default_scope { where(color: 'red') }

The former has numerous issues. It is a common newbie gotcha to do
the following:

    scope :recent, where(published_at: Time.now - 2.weeks)

Or a more subtle variant:

    scope :recent, -> { where(published_at: Time.now - 2.weeks) }
    scope :recent_red, recent.where(color: 'red')

Eager scopes are also very complex to implement within Active
Record, and there are still bugs. For example, the following does
not do what you expect:

    scope :remove_conditions, except(:where)
    where(...).remove_conditions # => still has conditions

scope is syntactic sugar for defining a class method. Ruby allows
redefining methods but emits a warning when run with -w. So let's
not implement our own logic for this. Users should run with -w if they
want to be warned about redefined methods.

Fix bug with autosave collection association on new record with a marked for destroy record in autosave collection.

add test to show offset query_methods on mysql & mysql2

change test to cover public API

make active_connection? return true only if there is an open connection in use for the current thread. fixes #5330

Add tests to test that through associations are not readonly, and we can update the records we retrive from the association

:strict

This apparently fix the warning related to @new_record variable not
being initialized in AR's test suit, when an association is built and
the object is marshalled/loaded.

See these tests in AR's base_test.rb:

test_marshalling_with_associations
test_marshalling_new_record_round_trip_with_associations

Closes #3720.