Fix at_exit hook to cooperate with Minitest

CHANGELOG.md

@@ -9,6 +9,7 @@ Unrealeased
 ## Bugfixes
 
 * Add new instance of `Minitest` constant. The `MiniTest` constant (with the capital T) will be removed in the next major release of Minitest.
+* Use `Minitest.after_run` hook to trigger post-run hooks if `Minitest` is present.
 
 0.17.1 (2019-09-16)
 ===================

lib/simplecov/defaults.rb

@@ -22,8 +22,18 @@
 SimpleCov::CommandGuesser.original_run_command = "#{$PROGRAM_NAME} #{ARGV.join(' ')}"
 
 at_exit do
+  if defined?(Minitest)
+    Minitest.after_run do
+      simplecov_at_exit
+    end
+  else
+    simplecov_at_exit
+  end
+end
+
+def simplecov_at_exit
   # If we are in a different process than called start, don't interfere.
-  next if SimpleCov.pid != Process.pid
+  return if SimpleCov.pid != Process.pid
 
   SimpleCov.set_exit_exception
   SimpleCov.run_exit_tasks!