Since #29572, minitest options are available but are no longer showed
in help.
This fixed to show minitest option in help as with Rails 5.1.2.
**before**
```
./bin/rails t --help
You can run a single test by appending a line number to a filename:
bin/rails test test/models/user_test.rb:27
You can run multiple files and directories at the same time:
bin/rails test test/controllers test/integration/login_test.rb
By default test failures and errors are reported inline during a run.
Rails options:
-w, --warnings Run with Ruby warnings enabled
-e, --environment Run tests in the ENV environment
-b, --backtrace Show the complete backtrace
-d, --defer-output Output test failures and errors after the test run
-f, --fail-fast Abort test run on first failure or error
-c, --[no-]color Enable color in the output
```
**after**
```
./bin/rails t --help
You can run a single test by appending a line number to a filename:
bin/rails test test/models/user_test.rb:27
You can run multiple files and directories at the same time:
bin/rails test test/controllers test/integration/login_test.rb
By default test failures and errors are reported inline during a run.
minitest options:
-h, --help Display this help.
-s, --seed SEED Sets random seed. Also via env. Eg: SEED=n rake
-v, --verbose Verbose. Show progress processing files.
-n, --name PATTERN Filter run on /regexp/ or string.
--exclude PATTERN Exclude /regexp/ or string from run.
Known extensions: rails, pride
-w, --warnings Run with Ruby warnings enabled
-e, --environment Run tests in the ENV environment
-b, --backtrace Show the complete backtrace
-d, --defer-output Output test failures and errors after the test run
-f, --fail-fast Abort test run on first failure or error
-c, --[no-]color Enable color in the output
-p, --pride Pride. Show your testing pride!
```
By making the Rails minitest behave like a standard minitest plugin
we're much more likely to not break when people use other minitest
plugins. Like minitest-focus and pride.
To do this, we need to behave like minitest: require files up front
and then perform the plugin behavior via the at_exit hook.
This also saves us a fair bit of wrangling with test file loading.
Finally, since the environment and warnings options have to be applied
as early as possible, and since minitest loads plugins at_exit, they
have to be moved to the test command.
* Don't expect the root method.
It's likely this worked because we eagerly loaded the Rails minitest plugin
and that somehow defined a root method on `Rails`.
* Assign a backtrace to failed exceptions.
Otherwise Minitest pukes when attempting to filter the backtrace (which
Rails' backtrace cleaner then removes).
Means the exception message test has to be revised too.
This is likely caused by the rails minitest plugin now being loaded for
these tests and assigning a default backtrace cleaner.
