Add link to minitest rdoc & github
[ci skip] Use appropriate mailer syntax.

Reference: https://github.com/rails/rails/commit/f7e4362011ceb1317fd401125d48d7ccb9a1079c
[ci skip] Remove duplicated last! section.

Reference: https://github.com/rails/rails/commit/d4fd0bd17709735ac91e434c94fe99429f078c6e

cc @schneems
Performed Returns true if redirect/render has happened
[ci skip] Normalize all localhost linking.
don't access named routes internals

just ask whether or not the route is defined
Redefine macro checks for reflections

Now that we define the macro on the reflection type we no longer
need to check `macro == :what` on each type for `belongs_to?` or
`has_one?` etc. These now default to false unless it's defined
in the reflection class.

Reuse existing belongs_to? method to check macros

We don't need to do `:belongs_to == macro` anymore becasue we
have a `belongs_to?` method. I didn't find this being used
anywhere for `has_one?` or `collection?` since they were already
fixed.
Removed unnecessary call to 'convert_key' in 'HashWithIndifferentAccess#to_hash'

All the keys are already Strings by virtue of being a HashWithIndifferentAccess.
turn scope in to a linked list

this makes scope rollback much easier
push options inside the scope object
remove useless deup

every call to default_resources_path_names allocates a new hash, no need
to dup
Remove some globals from configuration tests
Fix / improve some assertions
Remove some more globals from tests

We are using blocks here so we have access to the environment around
them, no need for globals.
Merge pull request #16352 from gchan/remove-unnecessary-convert-key

Removed unnecessary call to 'convert_key' in 'HashWithIndifferentAccess#to_hash'
Invert unless..else conditions on JRuby checks
Simplify plugin tests a bit, leave the regexp work for minitest
Simplify path setup
Use default argument when testing generators without the need for extra args
Avoid defining the test if it does not need to when not on JRuby