```ruby
require 'spec_helper'
require 'support/db'

class Post < ShardHandler::Model
end

describe ShardHandler do
  before(:all) do
    Db.setup

    Db.connect_to_shard('shard1')
    silence_stream(STDOUT) do
      load('spec/support/shard_schema.rb')
    end
    Db.connection.execute <<-SQL
      INSERT INTO posts (title) VALUES ('post from shard1')
    SQL

    Db.connect_to_shard('shard2')
    silence_stream(STDOUT) do
      load('spec/support/shard_schema.rb')
    end
    Db.connection.execute <<-SQL
      INSERT INTO posts (title) VALUES ('post from shard2')
    SQL

    Db.connect_to_root
  end

  after(:all) do
    Db.teardown
  end

  before do
    described_class.setup(Db.shards_config)
  end

  after do
    described_class.disconnect_all
  end

  context 'no shard set' do
    it 'raises an error' do
      expect do
        Post.all.to_a
      end.to raise_error(ActiveRecord::StatementInvalid, /PG::UndefinedTable/)
    end
  end

  context 'shard set' do
    it 'executes the query on the selected shard' do
      described_class.using('shard1') do
        expect(Post.pluck(:title)).to eql(['post from shard1'])
      end

      described_class.using('shard2') do
        expect(Post.pluck(:title)).to eql(['post from shard2'])
      end
    end
  end
end
```

Test inherited class on integration spec
user
```ruby
require 'spec_helper'
require 'support/db'

class Post < ShardHandler::Model
end

describe ShardHandler do
  before(:all) do
    Db.setup

    Db.connect_to_shard('shard1')
    silence_stream(STDOUT) do
      load('spec/support/shard_schema.rb')
    end
    Db.connection.execute <<-SQL
      INSERT INTO posts (title) VALUES ('post from shard1')
    SQL

    Db.connect_to_shard('shard2')
    silence_stream(STDOUT) do
      load('spec/support/shard_schema.rb')
    end
    Db.connection.execute <<-SQL
      INSERT INTO posts (title) VALUES ('post from shard2')
    SQL

    Db.connect_to_root
  end

  after(:all) do
    Db.teardown
  end

  before do
    Post.setup(Db.shards_config)
  end

  after do
    Post.handler.disconnect_all
  end

  context 'no shard set' do
    it 'raises an error' do
      expect do
        Post.all.to_a
      end.to raise_error(ActiveRecord::StatementInvalid, /PG::UndefinedTable/)
    end
  end

  context 'shard set' do
    it 'executes the query on the selected shard' do
      Post.using('shard1') do
        expect(Post.pluck(:title)).to eql(['post from shard1'])
      end

      Post.using('shard2') do
        expect(Post.pluck(:title)).to eql(['post from shard2'])
      end
    end
  end
end
```
assistant