1 files changed, 54 insertions, 0 deletions
diff --git a/spec/lib/gitlab/repository_cache/preloader_spec.rb b/spec/lib/gitlab/repository_cache/preloader_spec.rb
new file mode 100644
index 00000000000..8c6618c9f8f
--- /dev/null
+++ b/spec/lib/gitlab/repository_cache/preloader_spec.rb
@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::RepositoryCache::Preloader, :use_clean_rails_redis_caching do
+  let(:projects) { create_list(:project, 2, :repository) }
+  let(:repositories) { projects.map(&:repository) }
+
+  describe '#preload' do
+    context 'when the values are already cached' do
+      before do
+        # Warm the cache but use a different model so they are not memoized
+        repos = Project.id_in(projects).order(:id).map(&:repository)
+
+        allow(repos[0].head_tree).to receive(:readme_path).and_return('README.txt')
+        allow(repos[1].head_tree).to receive(:readme_path).and_return('README.md')
+
+        repos.map(&:exists?)
+        repos.map(&:readme_path)
+      end
+
+      it 'prevents individual cache reads for cached methods' do
+        expect(Rails.cache).to receive(:read_multi).once.and_call_original
+
+        described_class.new(repositories).preload(
+          %i[exists? readme_path]
+        )
+
+        expect(Rails.cache).not_to receive(:read)
+        expect(Rails.cache).not_to receive(:write)
+
+        expect(repositories[0].exists?).to eq(true)
+        expect(repositories[0].readme_path).to eq('README.txt')
+
+        expect(repositories[1].exists?).to eq(true)
+        expect(repositories[1].readme_path).to eq('README.md')
+      end
+    end
+
+    context 'when values are not cached' do
+      it 'reads and writes from cache individually' do
+        described_class.new(repositories).preload(
+          %i[exists? has_visible_content?]
+        )
+
+        expect(Rails.cache).to receive(:read).exactly(4).times
+        expect(Rails.cache).to receive(:write).exactly(4).times
+
+        repositories.each(&:exists?)
+        repositories.each(&:has_visible_content?)
+      end
+    end
+  end
+end