1 files changed, 57 insertions, 0 deletions
diff --git a/spec/models/concerns/loose_index_scan_spec.rb b/spec/models/concerns/loose_index_scan_spec.rb
new file mode 100644
index 00000000000..685819bfb86
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+++ b/spec/models/concerns/loose_index_scan_spec.rb
@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+# frozen_string_literal
+
+require 'spec_helper'
+
+RSpec.describe LooseIndexScan, type: :model do
+  let(:issue_model) do
+    Class.new(ApplicationRecord) do
+      include LooseIndexScan
+
+      self.table_name = 'issues'
+    end
+  end
+
+  let_it_be(:user_1) { create(:user) }
+  let_it_be(:user_2) { create(:user) }
+  let_it_be(:user_3) { create(:user) }
+
+  let_it_be(:issue_1) { create(:issue, author: user_2) }
+  let_it_be(:issue_2) { create(:issue, author: user_1) }
+  let_it_be(:issue_3) { create(:issue, author: user_1) }
+  let_it_be(:issue_4) { create(:issue, author: user_2) }
+  let_it_be(:issue_5) { create(:issue, author: user_3) }
+
+  context 'loading distinct author_ids' do
+    subject(:author_ids) { issue_model.loose_index_scan(column: :author_id, order: order).pluck(:author_id) }
+
+    shared_examples 'assert distinct values example' do
+      it 'loads the distinct values in the correct order' do
+        expect(author_ids).to eq(expected_order)
+      end
+    end
+
+    context 'when using ascending order' do
+      let(:order) { :asc }
+      let(:expected_order) { [user_1.id, user_2.id, user_3.id] }
+
+      it_behaves_like 'assert distinct values example'
+
+      context 'when null values are present' do
+        before do
+          issue_1.author_id = nil
+          issue_1.save!(validate: false)
+        end
+
+        it_behaves_like 'assert distinct values example'
+      end
+
+      context 'when using descending order' do
+        let(:order) { :desc }
+        let(:expected_order) { [user_3.id, user_2.id, user_1.id] }
+
+        it_behaves_like 'assert distinct values example'
+      end
+    end
+  end
+end