`yield` was missing in #with_dup, due to which 57 assertions were not running
in real, and all tests were passing by default.
Error was introduced in commit - 31ceb5e6.

Minitest has already been required when calling Minitest.autorun.

`Array#to` is working for negative position

We need to test if the same method defined more than once only register
one subscriber for it. We can safelly remove because the method body is
the same and Subscriber use method_added hook for register the
subscriber.

Just moved class methods up in file and moved `def self.` methods into `class << self`.

This deprecation was released in 4.1.0 and can be removed for 4.2.0,
deprecation message / handling is no longer necessary.

Use if/else instead of unless/else so conditional reads better.

Removed `FIMXE` tag to require necessary file but not the whole core_ext

- Fix `test_to_with_instruct` typo to `test_to_xml_with_instruct`

- Rename `test_to_xml` to `test_to_xml_with_hash_elements` to make test
name more specific.

- Add `test_to_xml_with_non_hash_elements` and
`test_to_xml_with_non_hash_different_type_elements`

  `to_xml` behaves different when containing elements are same and
  different types.

- Add `test_to_xml_with_indent_set`

Require active_support/core_ext/string/output_safety and use html_safe rather than use non-public SafeBuffer API.

Use block parameter rather than `$1` during `gsub!` so `ActiveSupport::SafeBuffer` values aren't mangled.

Fixes #15064

Namely, if the mday is omitted but any other upper components are, then instead
of supplying the mday from the current time, it defaults to 1.

Current docs are wrong. Does not accept strftime inputs.

ActiveSupport::Subscriber no longer creates multiple subscribers when
you redefine a method.

* Strips leading underscores.
* Changes some unnecessary gsub!s to sub!s.
* Replaces some anchors ^, $ with \A, \z.
* Documents that human inflection rules are applied.
* Documents that words are downcased except acronyms.
* Adds an example with an acronym.
* Rewords docs.

Empty Hash or Array should not present in serialization result

    {a: []}.to_query # => ""
    {a: {}}.to_query # => ""

For more info see #14948.

After this 21dbe6f3

2.1.1 :001 > 'business'.classify
 => "Business"

2.1.1 :004 > 'calculus'.classify
 => "Calculu"
2.1.1 :005 >

Before:
  When calling String#pluralize with count=1 then it returned same
  string, but with count other than 1, returned new string.

After:
  String#pluralize always return a new string.

  => Prevent mutation of a string inadvertently.

While calling String#first or String#last with zero or a Fixnum < the
string's length returns a new string, a Fixnum >= the string's length
returns the string itself. This inconsistency can lead to inadvertent
mutation of a string.

1. Improve tests
2. Remove unnecessary constant
3. Add docs for BigDecimal#duplicable?

[ci skip]