Testing: Speed up Twitter tests by paring down VCR cassette content

This commit reduces the execution time of the specs for
Channel::Driver::Twitter#fetch by a little over 50%.

The #fetch method calls out to the Twitter API
and receives a list of tweets (serialized as JSON),
then converts them to tickets and articles.
Even with HTTP caching (via VCR), this is an expensive operation:
each transaction may contain dozens of tweets to be processed.

This commit reduces the processing burden
by manually editing the tests' VCR cassettes,
removing the vast majority of incoming tweets
and keeping only those necessary to run meaningful tests.

The result is a set of tests for the #fetch method that,
on a given machine, now take 65 seconds instead of 140.
As an ancillary benefit, the file size of the associated
VCR cassette directory has been reduced from 16MB to under 5MB.

spec/models/channel/driver/twitter_spec.rb

@@ -821,7 +821,7 @@ RSpec.describe Channel::Driver::Twitter do
       context 'with search term configured (at .options[:sync][:search])' do
         it 'creates an article for each recent tweet' do
           expect { channel.fetch }
-            .to change(Ticket, :count).by(8)
+            .to change(Ticket, :count).by(2)
 
           expect(Ticket.last.attributes).to include(
             'title'       => "Come and join our team to bring Zammad even further forward!   It's gonna be ama...",
@@ -831,115 +831,87 @@ RSpec.describe Channel::Driver::Twitter do
           )
         end
 
+        context 'for responses to other tweets' do
+          let(:thread) do
+            Ticket.joins(articles: :type).where(ticket_article_types: { name: 'twitter status' })
+              .group('tickets.id').having(
+                case ActiveRecord::Base.connection_config[:adapter]
+                when 'mysql2'
+                  'COUNT("ticket_articles.*") > 1'
+                when 'postgresql'
+                  'COUNT(ticket_articles.*) > 1'
+                end
+              ).first
+          end
+
+          it 'creates articles for parent tweets as well' do
+            channel.fetch
+
+            expect(thread.articles.last.body).to match(/zammad/i)       # search result
+            expect(thread.articles.first.body).not_to match(/zammad/i)  # parent tweet
+          end
+        end
+
+        context 'and "track_retweets" option' do
+          context 'is false (default)' do
             it 'skips retweets' do
               expect { channel.fetch }
                 .not_to change { Ticket.where('title LIKE ?', 'RT @%').count }.from(0)
             end
-
-        it 'skips tweets 15+ days older than channel itself' do
-          expect { channel.fetch }
-            .not_to change { Ticket.where('title LIKE ?', 'GitHub Trending Archive, 2_ Nov 2018, Ruby. %').count }.from(0)
           end
 
+          context 'is true' do
+            subject(:channel) { create(:twitter_channel, custom_options: { sync: { track_retweets: true } }) }
+
+            it 'creates an article for each recent tweet/retweet' do
+              expect { channel.fetch }
+                .to change { Ticket.where('title LIKE ?', 'RT @%').count }.by(1)
+                .and change(Ticket, :count).by(3)
+            end
+          end
+        end
+
+        context 'and "import_older_tweets" option (legacy)' do
+          context 'is false (default)' do
+            it 'skips tweets 15+ days older than channel itself' do
+              expect { channel.fetch }
+                .not_to change { Ticket.where('title LIKE ?', 'GitHub Trending Archive, 29 Nov 2018, Ruby. %').count }.from(0)
+            end
+          end
+
+          context 'is true' do
+            subject(:channel) { create(:twitter_channel, :legacy) }
+
+            it 'creates an article for each tweet' do
+              expect { channel.fetch }
+                .to change { Ticket.where('title LIKE ?', 'GitHub Trending Archive, 29 Nov 2018, Ruby. %').count }.by(1)
+                .and change(Ticket, :count).by(3)
+            end
+          end
+        end
+
+        describe 'duplicate handling' do
           context 'when fetched tweets have already been imported' do
             before do
               tweet_ids.each { |tweet_id| create(:ticket_article, message_id: tweet_id) }
             end
 
-          let(:tweet_ids) do
+            let(:tweet_ids) { [1222126386334388225, 1222109934923460608] }  # rubocop:disable Style/NumericLiterals
-            [1224440380881428480,
-             1224426978557800449,
-             1224427517869809666,
-             1224427776654135297,
-             1224428510225354753,
-             1223188240078909440,
-             1223273797987508227,
-             1223103807283810304,
-             1223121619561799682,
-             1222872891320143878,
-             1222881209384161283,
-             1222896407524212736,
-             1222237955588227075,
-             1222108036795334657,
-             1222126386334388225,
-             1222109934923460608]
-          end
 
             it 'does not import duplicates' do
               expect { channel.fetch }.not_to change(Ticket::Article, :count)
             end
           end
 
-        context 'for very common search terms' do
-          subject(:channel) { create(:twitter_channel, custom_options: custom_options) }
-
-          let(:custom_options) do
-            {
-              sync: {
-                search: [
-                  {
-                    term:     'coronavirus',
-                    group_id: Group.first.id
-                  }
-                ]
-              }
-            }
-          end
-
-          let(:twitter_articles) { Ticket::Article.joins(:type).where(ticket_article_types: { name: 'twitter status' }) }
-
-          it 'stops importing threads after 120 new articles' do
-            channel.fetch
-
-            expect((twitter_articles - Ticket.last.articles).count).to be < 120
-            expect(twitter_articles.count).to be >= 120
-          end
-
-          it 'refuses to import any other tweets for the next 15 minutes' do
-            channel.fetch
-            travel(14.minutes)
-
-            expect { create(:twitter_channel).fetch }
-              .not_to change(Ticket::Article, :count)
-          end
-
-          it 'resumes importing again after 15 minutes' do
-            channel.fetch
-            travel(15.minutes)
-
-            expect { create(:twitter_channel).fetch }
-              .to change(Ticket::Article, :count)
-          end
-        end
-
-        context 'and "track_retweets" option' do
-          subject(:channel) { create(:twitter_channel, custom_options: { sync: { track_retweets: true } }) }
-
-          it 'creates an article for each recent tweet/retweet' do
-            expect { channel.fetch }
-              .to change { Ticket.where('title LIKE ?', 'RT @%').count }
-              .and change(Ticket, :count).by(21)
-          end
-        end
-
-        context 'and "import_older_tweets" option (legacy)' do
-          subject(:channel) { create(:twitter_channel, :legacy) }
-
-          it 'creates an article for each tweet' do
-            expect { channel.fetch }
-              .to change { Ticket.where('title LIKE ?', 'GitHub Trending Archive, 2_ Nov 2018, Ruby. %').count }
-              .and change(Ticket, :count).by(21)
-          end
-        end
-
           describe 'Race condition: when #fetch finds a half-processed, outgoing tweet' do
             subject!(:channel) { create(:twitter_channel, custom_options: custom_options) }
 
             let(:custom_options) do
               {
                 user: {
-                # Must match outgoing tweet author Twitter user ID
+                  # Must match connected Twitter account's user ID (on Twitter)--
-                id: '1205290247124217856',
+                  # that's how #fetch distinguishes between agents' tweets and other people's.
+                  id: '1205290247124217856'
                 },
                 sync: {
                   search: [
@@ -995,6 +967,47 @@ RSpec.describe Channel::Driver::Twitter do
             end
           end
         end
+
+        context 'for very common search terms' do
+          subject(:channel) { create(:twitter_channel, custom_options: custom_options) }
+
+          let(:custom_options) do
+            {
+              sync: {
+                search: [
+                  {
+                    term:     'coronavirus',
+                    group_id: Group.first.id
+                  }
+                ]
+              }
+            }
+          end
+
+          let(:twitter_articles) { Ticket::Article.joins(:type).where(ticket_article_types: { name: 'twitter status' }) }
+
+          # NOTE: Ordinarily, RSpec examples should be kept as small as possible.
+          # In this case, we bundle these examples together because
+          # separating them would duplicate expensive setup:
+          # even with HTTP caching, this single example takes nearly a minute.
+          it 'imports max. ~120 articles every 15 minutes' do
+            channel.fetch
+
+            expect((twitter_articles - Ticket.last.articles).count).to be <= 120
+            expect(twitter_articles.count).to be > 120
+
+            travel(14.minutes)
+
+            expect { create(:twitter_channel).fetch }
+              .not_to change(Ticket::Article, :count)
+
+            travel(1.minute)
+
+            expect { create(:twitter_channel).fetch }
+              .to change(Ticket::Article, :count)
+          end
+        end
+      end
     end
   end
 end