Always define SimpleCov.external_at_exit

See no reason not to, makes it easier and everything that we
remove from defaults seems worthwhile.

Author: PragTob

lib/minitest/simplecov_plugin.rb

@@ -4,7 +4,7 @@
 # https://github.com/seattlerb/minitest#writing-extensions
 module Minitest
   def self.plugin_simplecov_init(_options)
-    SimpleCov.external_at_exit = true if SimpleCov.respond_to?(:external_at_exit=)
+    SimpleCov.external_at_exit = true
 
     Minitest.after_run do
       SimpleCov.at_exit_behavior if SimpleCov.respond_to?(:at_exit_behavior)

lib/simplecov.rb

@@ -27,6 +27,11 @@ class << self
     attr_accessor :pid
     attr_reader :exit_exception
 
+    # Basically, should we take care of at_exit behavior or something else?
+    # Used by the minitest plugin. See lib/minitest/simplecov_plugin.rb
+    attr_accessor :external_at_exit
+    alias external_at_exit? external_at_exit
+
     #
     # Sets up SimpleCov to run against your project.
     # You can optionally specify a profile to use as well as configuration with a block:

lib/simplecov/defaults.rb

@@ -21,11 +21,6 @@
 # Gotta stash this a-s-a-p, see the CommandGuesser class and i.e. #110 for further info
 SimpleCov::CommandGuesser.original_run_command = "#{$PROGRAM_NAME} #{ARGV.join(' ')}"
 
-class << SimpleCov
-  attr_accessor :external_at_exit
-  alias external_at_exit? external_at_exit
-end
-
 at_exit do
   next if SimpleCov.external_at_exit?