Connection pool swapping back to the AR::Base pool requires new step as of rails commit fcb223d (merge of #24844)

test_for_swapping_connection_pools.diff

diff --git a/activerecord/test/cases/connection_adapters/connection_handler_test.rb b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
index fc5ca88..d171ea7 100644
--- a/activerecord/test/cases/connection_adapters/connection_handler_test.rb
+++ b/activerecord/test/cases/connection_adapters/connection_handler_test.rb
@@ -21,6 +21,34 @@ def test_establish_connection_uses_spec_name
         @handler.remove_connection('readonly')
       end

+      def test_a_class_using_custom_pool_and_switching_back_to_primary
+        klass2     = Class.new(Base)   { def self.name; 'klass2'; end }
+
+        # AR::Base's primary connection pool has a size of 5 by default
+        connection = klass2.connection
+        assert_equal(connection.pool.size, 5)
+
+        # Create a new pool for this class using pool 10
+        pool = klass2.establish_connection(adapter: 'sqlite3', pool: 10, :database => "activerecord_unittest")
+        begin
+          conn = pool.connection
+          assert_equal(conn.pool.size, 10)
+        ensure
+          # Drop the customized connection pool
+          klass2.remove_connection
+
+          # Either of the two lines below fixes this test on master/5-0-stable
+          # but are not obvious. Should remove_connection being doing this?
+          # Is this a change in behavior we need to warn about?  
+          # They are not required prior to fcb223d (merge of #24844).
+          #
+          # klass2.establish_connection
+          # klass2.connection_specification_name = "primary"
+
+          # Verify, we're back to the default pool size of 5
+          assert_equal(klass2.connection.pool.size, 5)
+        end
+      end
+
       def test_retrieve_connection
         assert @handler.retrieve_connection(@spec_name)
       end

z_5_0_stable_at_3eb70d0_output.log

11:34:56 ~/Code/rails/activerecord (master) (2.2.4) + git checkout 5-0-stable
...
11:34:59 ~/Code/rails/activerecord (5-0-stable) (2.2.4) + git pull
Current branch 5-0-stable is up to date.
11:35:56 ~/Code/rails/activerecord (5-0-stable) (2.2.4) - bundle
...

11:36:05 ~/Code/rails/activerecord (5-0-stable) (2.2.4) + be ruby -Itest -I test test/cases/connection_adapters/connection_handler_test.rb
Using postgresql
Run options: --seed 30039

# Running:

........E

Finished in 0.120750s, 74.5342 runs/s, 107.6605 assertions/s.

  1) Error:
ActiveRecord::ConnectionAdapters::ConnectionHandlerTest#test_a_class_using_custom_pool_and_switching_back_to_primary:
ActiveRecord::ConnectionNotEstablished: No connection pool with id klass2 found.
    /Users/joerafaniello/Code/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb:876:in `retrieve_connection'
    /Users/joerafaniello/Code/rails/activerecord/lib/active_record/connection_handling.rb:128:in `retrieve_connection'
    /Users/joerafaniello/Code/rails/activerecord/lib/active_record/connection_handling.rb:91:in `connection'
    test/cases/connection_adapters/connection_handler_test.rb:49:in `test_a_class_using_custom_pool_and_switching_back_to_primary'

9 runs, 13 assertions, 0 failures, 1 errors, 0 skips

z_5_0_stable_prior_to_24844.log

11:39:16 ~/Code/rails/activerecord (5-0-stable) (2.2.4) - git checkout fcb223dd53f75bc299c267341d09791be822b0a9~
...
11:39:22 ~/Code/rails/activerecord ((bf876aa...)) (2.2.4) + be ruby -Itest -I test test/cases/connection_adapters/connection_handler_test.rb
Using postgresql
Run options: --seed 8128

# Running:

..........

Finished in 0.121621s, 82.2226 runs/s, 131.5562 assertions/s.

10 runs, 16 assertions, 0 failures, 0 errors, 0 skips