Reset the db connections

docker-compose.ci.yml

@@ -5,7 +5,6 @@ services:
   ci:
     environment:
       - ACTIVERECORD_UNITTEST_HOST=sqlserver
-      - SQLSERVER_CI=true
     build:
       context: .
       dockerfile: Dockerfile.ci

test/cases/transaction_test_sqlserver.rb

@@ -54,8 +54,6 @@ class TransactionTestSQLServer < ActiveRecord::TestCase
 
   describe "when READ_COMMITTED_SNAPSHOT is set" do
     it "should use READ COMMITTED as an isolation level" do
-      skip "This test sometimes causes subsequent tests to fail with error 'DBPROCESS is dead or not enabled'. The test passes if run alone." if ENV["SQLSERVER_CI"]
-
       connection.execute "ALTER DATABASE [#{connection.current_database}] SET ALLOW_SNAPSHOT_ISOLATION ON"
       connection.execute "ALTER DATABASE [#{connection.current_database}] SET READ_COMMITTED_SNAPSHOT ON WITH ROLLBACK IMMEDIATE"
 
@@ -69,10 +67,12 @@ class TransactionTestSQLServer < ActiveRecord::TestCase
       # "READ COMMITTED", and that no exception was raised (it's reported back
       # by SQL Server as "read committed snapshot").
       _(connection.user_options_isolation_level).must_match "read committed snapshot"
-
     ensure
       connection.execute "ALTER DATABASE [#{connection.current_database}] SET ALLOW_SNAPSHOT_ISOLATION OFF"
       connection.execute "ALTER DATABASE [#{connection.current_database}] SET READ_COMMITTED_SNAPSHOT OFF WITH ROLLBACK IMMEDIATE"
+
+      # Reset all connections. Otherwise, the next test may fail with error 'DBPROCESS is dead or not enabled'. Not sure why.
+      ActiveRecord::Base.connection_handler.clear_all_connections!
     end
   end