Add integration tests for index groups.
user
```ruby
require "integration_test_helper"
require "rest-client"
require "cgi"

class ElasticsearchIndexGroupTest < IntegrationTest

  def setup
    @group_name = "rummager_test"
    stub_elasticsearch_settings [@group_name]
    enable_test_index_connections
    try_remove_test_index

    @index_group = search_server.index_group(@group_name)
  end

  def teardown
    clean_index_group @group_name
  end

  def test_should_create_index
    assert @index_group.index_names.empty?
    index = @index_group.create_index

    assert_equal 1, @index_group.index_names.count
    assert_equal index.index_name, @index_group.index_names[0]
    assert_equal(
      app.settings.elasticsearch_schema["mappings"]["default"],
      index.mappings
    )
  end

  def test_should_alias_index
    index = @index_group.create_index
    @index_group.switch_to(index)

    assert_equal index.real_name, @index_group.current.real_name
  end

  def test_should_switch_index
    old_index = @index_group.create_index
    @index_group.switch_to(old_index)

    new_index = @index_group.create_index
    @index_group.switch_to(new_index)

    assert_equal new_index.real_name, @index_group.current.real_name
  end

  def test_should_clean_indices
    @index_group.create_index
    @index_group.switch_to(@index_group.create_index)

    assert_equal 2, @index_group.index_names.count
    @index_group.clean
    assert_equal 1, @index_group.index_names.count
  end
end
```
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