fix deploy problems due to renamed table

spec/components/table_migration_helper_spec.rb

@@ -0,0 +1,66 @@
+require 'rails_helper'
+require 'table_migration_helper'
+
+describe TableMigrationHelper do
+
+  def table_exists?(table_name)
+    sql = <<-SQL
+    SELECT 1
+    FROM INFORMATION_SCHEMA.TABLES
+    WHERE table_schema = 'public' AND
+          table_name = '#{table_name}'
+    SQL
+
+    ActiveRecord::Base.exec_sql(sql).to_a.length > 0
+  end
+
+  describe '#delayed_drop' do
+    it "can drop a table after correct delay and when new table exists" do
+      ActiveRecord::Base.exec_sql "CREATE TABLE table_with_old_name (topic_id INTEGER)"
+
+      name = ActiveRecord::Base
+              .exec_sql("SELECT name FROM schema_migration_details LIMIT 1")
+              .getvalue(0,0)
+
+      Topic.exec_sql("UPDATE schema_migration_details SET created_at = :created_at WHERE name = :name",
+                    name: name, created_at: 15.minutes.ago)
+
+      dropped_proc_called = false
+
+      described_class.delayed_drop(
+        old_name: 'table_with_old_name',
+        new_name: 'table_with_new_name',
+        after_migration: name,
+        delay: 20.minutes,
+        on_drop: ->(){dropped_proc_called = true}
+      )
+
+      expect(table_exists?('table_with_old_name')).to eq(true)
+      expect(dropped_proc_called).to eq(false)
+
+      described_class.delayed_drop(
+        old_name: 'table_with_old_name',
+        new_name: 'table_with_new_name',
+        after_migration: name,
+        delay: 10.minutes,
+        on_drop: ->(){dropped_proc_called = true}
+      )
+
+      expect(table_exists?('table_with_old_name')).to eq(true)
+      expect(dropped_proc_called).to eq(false)
+
+      ActiveRecord::Base.exec_sql "CREATE TABLE table_with_new_name (topic_id INTEGER)"
+
+      described_class.delayed_drop(
+        old_name: 'table_with_old_name',
+        new_name: 'table_with_new_name',
+        after_migration: name,
+        delay: 10.minutes,
+        on_drop: ->(){dropped_proc_called = true}
+      )
+
+      expect(table_exists?('table_with_old_name')).to eq(false)
+      expect(dropped_proc_called).to eq(true)
+    end
+  end
+end