Coerce test an empty transaction does not raise if preventing writes. (#788)

The transaction in the test become SavepointTransaction  because tests automatically wrapped in transaction,
and SQL Server does not have query for release_savepoint

Author: YehudaGold

test/cases/coerced_tests.rb

@@ -177,6 +177,18 @@ def test_update_date_time_attributes_with_default_timezone_local
       end
     end
   end
+
+  # SQL Server does not have query for release_savepoint
+  coerce_tests! %r{an empty transaction does not raise if preventing writes}
+  test "an empty transaction does not raise if preventing writes coerced" do
+    ActiveRecord::Base.connection_handler.while_preventing_writes do
+      assert_queries(1, ignore_none: true) do
+        Bird.transaction do
+          ActiveRecord::Base.connection.materialize_transactions
+        end
+      end
+    end
+  end
 end