discourse/spec/services/random_topic_selector_spec.rb

require 'rails_helper'

describe RandomTopicSelector do

  it 'can correctly use cache' do
    key = RandomTopicSelector.cache_key

    $redis.del key

    4.times do |t|
      $redis.rpush key, t
    end

    expect(RandomTopicSelector.next(0)).to eq([])
    expect(RandomTopicSelector.next(2)).to eq([0, 1])

    $redis.expects(:multi).returns(Discourse.received_readonly!)
    expect(RandomTopicSelector.next(2)).to eq([2, 3])
    $redis.unstub(:multi)

    expect(RandomTopicSelector.next(2)).to eq([2, 3])
    expect(RandomTopicSelector.next(2)).to eq([])
  end

  it 'can correctly backfill' do
    category = Fabricate(:category, sort_order: 'op_likes')
    t1 = Fabricate(:topic, category_id: category.id)
    _t2 = Fabricate(:topic, category_id: category.id, visible: false)
    _t3 = Fabricate(:topic, category_id: category.id, deleted_at: 1.minute.ago)
    t4 = Fabricate(:topic, category_id: category.id)

    expect(RandomTopicSelector.next(5, category).sort).to eq([t1.id, t4.id].sort)
  end
end