1 files changed, 120 insertions, 0 deletions
diff --git a/spec/lib/gitlab/pagination/keyset/paginator_spec.rb b/spec/lib/gitlab/pagination/keyset/paginator_spec.rb
new file mode 100644
index 00000000000..3c9a8913876
--- /dev/null
+++ b/spec/lib/gitlab/pagination/keyset/paginator_spec.rb
@@ -0,0 +1,120 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Pagination::Keyset::Paginator do
+  let_it_be(:project_1) { create(:project, created_at: 10.weeks.ago) }
+  let_it_be(:project_2) { create(:project, created_at: 2.weeks.ago) }
+  let_it_be(:project_3) { create(:project, created_at: 3.weeks.ago) }
+  let_it_be(:project_4) { create(:project, created_at: 5.weeks.ago) }
+  let_it_be(:project_5) { create(:project, created_at: 2.weeks.ago) }
+
+  describe 'pagination' do
+    let(:per_page) { 10 }
+    let(:cursor) { nil }
+    let(:scope) { Project.order(created_at: :asc, id: :asc) }
+    let(:expected_order) { [project_1, project_4, project_3, project_2, project_5] }
+
+    subject(:paginator) { scope.keyset_paginate(cursor: cursor, per_page: per_page) }
+
+    context 'when per_page is greater than the record count' do
+      it { expect(paginator.records).to eq(expected_order) }
+      it { is_expected.not_to have_next_page }
+      it { is_expected.not_to have_previous_page }
+
+      it 'has no next and previous cursor values' do
+        expect(paginator.cursor_for_next_page).to be_nil
+        expect(paginator.cursor_for_previous_page).to be_nil
+      end
+    end
+
+    context 'when 0 records are returned' do
+      let(:scope) { Project.where(id: non_existing_record_id).order(created_at: :asc, id: :asc) }
+
+      it { expect(paginator.records).to be_empty }
+      it { is_expected.not_to have_next_page }
+      it { is_expected.not_to have_previous_page }
+    end
+
+    context 'when page size is smaller than the record count' do
+      let(:per_page) { 2 }
+
+      it { expect(paginator.records).to eq(expected_order.first(2)) }
+      it { is_expected.to have_next_page }
+      it { is_expected.not_to have_previous_page }
+
+      it 'has next page cursor' do
+        expect(paginator.cursor_for_next_page).not_to be_nil
+      end
+
+      it 'does not have previous page cursor' do
+        expect(paginator.cursor_for_previous_page).to be_nil
+      end
+
+      context 'when on the second page' do
+        let(:cursor) { scope.keyset_paginate(per_page: per_page).cursor_for_next_page }
+
+        it { expect(paginator.records).to eq(expected_order[2...4]) }
+        it { is_expected.to have_next_page }
+        it { is_expected.to have_previous_page }
+
+        context 'and then going back to the first page' do
+          let(:previous_page_cursor) { scope.keyset_paginate(cursor: cursor, per_page: per_page).cursor_for_previous_page }
+
+          subject(:paginator) { scope.keyset_paginate(cursor: previous_page_cursor, per_page: per_page) }
+
+          it { expect(paginator.records).to eq(expected_order.first(2)) }
+          it { is_expected.to have_next_page }
+          it { is_expected.not_to have_previous_page }
+        end
+      end
+
+      context 'when jumping to the last page' do
+        let(:cursor) { scope.keyset_paginate(per_page: per_page).cursor_for_last_page }
+
+        it { expect(paginator.records).to eq(expected_order.last(2)) }
+        it { is_expected.not_to have_next_page }
+        it { is_expected.to have_previous_page }
+
+        context 'when paginating backwards' do
+          let(:previous_page_cursor) { scope.keyset_paginate(cursor: cursor, per_page: per_page).cursor_for_previous_page }
+
+          subject(:paginator) { scope.keyset_paginate(cursor: previous_page_cursor, per_page: per_page) }
+
+          it { expect(paginator.records).to eq(expected_order[-4...-2]) }
+          it { is_expected.to have_next_page }
+          it { is_expected.to have_previous_page }
+        end
+
+        context 'when jumping to the first page' do
+          let(:first_page_cursor) { scope.keyset_paginate(cursor: cursor, per_page: per_page).cursor_for_first_page }
+
+          subject(:paginator) { scope.keyset_paginate(cursor: first_page_cursor, per_page: per_page) }
+
+          it { expect(paginator.records).to eq(expected_order.first(2)) }
+          it { is_expected.to have_next_page }
+          it { is_expected.not_to have_previous_page }
+        end
+      end
+    end
+
+    describe 'default keyset direction parameter' do
+      let(:cursor_converter_class) { Gitlab::Pagination::Keyset::Paginator::Base64CursorConverter }
+      let(:per_page) { 2 }
+
+      it 'exposes the direction parameter in the cursor' do
+        cursor = paginator.cursor_for_next_page
+
+        expect(cursor_converter_class.parse(cursor)[:_kd]).to eq(described_class::FORWARD_DIRECTION)
+      end
+    end
+  end
+
+  context 'when unsupported order is given' do
+    it 'raises error' do
+      scope = Project.order(path: :asc, name: :asc, id: :desc) # Cannot build 3 column order automatically
+
+      expect { scope.keyset_paginate }.to raise_error(/does not support keyset pagination/)
+    end
+  end
+end