Default to sorting user's test cases for now

Goals:

1. Default to :random for newly generated applications
2. Default to :sorted for existing applications with a warning
3. Only show the warning once
4. Only show the warning if the app actually uses AS::TestCase

Fixes #16769

1 files changed, 32 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/test_case.rb b/activesupport/lib/active_support/test_case.rb
index 0df599b692..33139320fa 100644
--- a/activesupport/lib/active_support/test_case.rb
+++ b/activesupport/lib/active_support/test_case.rb
@@ -12,10 +12,42 @@ require 'active_support/core_ext/kernel/reporting'
 require 'active_support/deprecation'
 
 module ActiveSupport
+  class << self
+    delegate :test_order, :test_order=, to: :'ActiveSupport::TestCase'
+  end
+
   class TestCase < ::Minitest::Test
     Assertion = Minitest::Assertion
 
+    @@test_order = nil
+
     class << self
+      def test_order=(new_order)
+        @@test_order = new_order
+      end
+
+      def test_order
+        if @@test_order.nil?
+          ActiveSupport::Deprecation.warn "You did not specify a value for the " \
+            "configuration option 'active_support.test_order'. In Rails 5.0, " \
+            "the default value of this option will change from `:sorted` to " \
+            "`:random`.\n" \
+            "To disable this warning and keep the current behavior, you can add " \
+            "the following line to your `config/environments/test.rb`:\n" \
+            "\n" \
+            "  Rails.application.configure do\n" \
+            "    config.active_support.test_order = :sorted\n" \
+            "  end\n" \
+            "\n" \
+            "Alternatively, you can opt into the future behavior by setting this " \
+            "option to `:random`."
+
+          @@test_order = :sorted
+        end
+
+        @@test_order
+      end
+
       alias :my_tests_are_order_dependent! :i_suck_and_my_tests_are_order_dependent!
     end