conversations_helper_spec.rb

...
context '#load_private_messages' do
  let(:conversation) { create(:private_conversation) }

  it "returns load_messages partial's path" do
    create(:private_message, conversation_id: conversation.id)
    expect(helper.load_private_messages(conversation)).to eq (
      'private/conversations/conversation/messages_list/link_to_previous_messages'
    )
  end

  it "returns empty partial's path" do
    expect(helper.load_private_messages(conversation)).to eq (
      'shared/empty_partial'
    )
  end
end
...