Added tests for issuable concern file

Added tests with scenario including milestones, releases and issues.
Fixed some scopes in issuable concern file.

app/finders/issuable_finder.rb

@@ -580,9 +580,9 @@ class IssuableFinder
   def by_release(items)
     if releases?
       items = if filter_by_no_release?
-                items.left_joins_milestones_joins_no_release
+                items.without_release
               elsif filter_by_any_release?
-                items.left_joins_milestones_joins_releases
+                items.any_release
               else
                 items.with_release(params[:release_tag])
               end

app/models/concerns/issuable.rb

@@ -123,19 +123,18 @@ module Issuable
     scope :order_milestone_due_desc, -> { left_joins_milestones.reorder(Arel.sql('milestones.due_date IS NULL, milestones.id IS NULL, milestones.due_date DESC')) }
     scope :order_milestone_due_asc,  -> { left_joins_milestones.reorder(Arel.sql('milestones.due_date IS NULL, milestones.id IS NULL, milestones.due_date ASC')) }
 
-    scope :left_joins_milestones_joins_no_release, -> do
-      joins("LEFT OUTER JOIN milestones
-               LEFT OUTER JOIN milestone_releases ON milestones.id = milestone_releases.milestone_id
-            ON #{table_name}.milestone_id = milestones.id"
-           ).where('milestone_releases.release_id IS NULL')
+    scope :without_release, -> do
+      joins("LEFT OUTER JOIN milestones AS ms ON #{table_name}.milestone_id = ms.id
+             LEFT OUTER JOIN milestone_releases AS ms_rl ON ms.id = ms_rl.milestone_id"
+           ).where('ms_rl.release_id IS NULL')
     end
 
     scope :left_joins_milestones_joins_releases, -> do
-      joins("LEFT OUTER JOIN milestones
+      joins("LEFT OUTER JOIN milestones AS ms
               JOIN milestone_releases
                 JOIN releases ON milestone_releases.release_id = releases.id
-              ON milestones.id = milestone_releases.milestone_id
-            ON #{table_name}.milestone_id = milestones.id"
+              ON ms.id = milestone_releases.milestone_id
+            ON #{table_name}.milestone_id = ms.id"
            ).where('milestone_releases.release_id IS NOT NULL').distinct
     end
 

spec/models/concerns/issuable_spec.rb

@@ -852,4 +852,125 @@ describe Issuable do
       it_behaves_like 'matches_cross_reference_regex? fails fast'
     end
   end
+
+  # Testing the release related scopes with the following setup:
+  # - release_1
+  #   - milestone_1
+  #     - issue_1
+  #     - issue_2
+  #   - milestone_2
+  #     - issue_3
+  #
+  # - release_2
+  #   - milestone_2
+  #     - issue_3
+  #   - milestone_3
+  #     - (no issue)
+  #
+  # - release_3
+  #   - milestone_4
+  #     - issue_4
+  #   - milestone_5
+  #     - issue_4
+  #
+  # - release_4
+  #   - milestone_3
+  #     - (no issue)
+  #
+  # - milestone_6 (no release)
+  #   - issue_5
+  #
+  # - issue_6 (no milestone, no release)
+
+  describe 'release scopes' do
+    let_it_be(:project) { create(:project) }
+
+    let_it_be(:release_1) { create(:release, tag: 'v1.0', project: project) }
+    let_it_be(:release_2) { create(:release, tag: 'v2.0', project: project) }
+    let_it_be(:release_3) { create(:release, tag: 'v3.0', project: project) }
+    let_it_be(:release_4) { create(:release, tag: 'v4.0', project: project) }
+
+    let_it_be(:milestone_1) { create(:milestone, title: 'm1', project: project) }
+    let_it_be(:milestone_2) { create(:milestone, title: 'm2', project: project) }
+    let_it_be(:milestone_3) { create(:milestone, title: 'm3', project: project) }
+    let_it_be(:milestone_4) { create(:milestone, title: 'm4', project: project) }
+    let_it_be(:milestone_5) { create(:milestone, title: 'm5', project: project) }
+    let_it_be(:milestone_6) { create(:milestone, title: 'm6', project: project) }
+
+    let_it_be(:issue_1) { create(:issue, project: project) }
+    let_it_be(:issue_2) { create(:issue, project: project) }
+    let_it_be(:issue_3) { create(:issue, project: project) }
+    let_it_be(:issue_4) { create(:issue, project: project) }
+    let_it_be(:issue_5) { create(:issue, project: project) }
+    let_it_be(:issue_6) { create(:issue, project: project) }
+
+    let_it_be(:items) { Issue.all }
+
+    before(:all) do
+      milestone_1.issues = [issue_1, issue_2]
+      milestone_2.issues = [issue_3]
+      milestone_4.issues = [issue_4]
+      milestone_5.issues = [issue_4]
+      milestone_6.issues = [issue_5]
+
+      release_1.milestones = [milestone_1, milestone_2]
+      release_2.milestones = [milestone_2, milestone_3]
+      release_3.milestones = [milestone_4, milestone_5]
+      release_4.milestones = [milestone_3]
+    end
+
+    describe '#without_release' do
+      it 'returns the issues not tied to any milestone and the ones tied to milestone with no release' do
+        expect(items.without_release).to contain_exactly(issue_5, issue_6)
+      end
+    end
+
+    describe '#any_release' do
+      it 'returns all issues tied to a release' do
+        expect(items.any_release).to contain_exactly(issue_1, issue_2, issue_3, issue_4)
+      end
+    end
+
+    describe '#with_release' do
+      it 'returns the issues tied a specfic release' do
+        expect(items.with_release('v1.0')).to contain_exactly(issue_1, issue_2, issue_3)
+      end
+
+      context 'when a release has a milestone with one issue and another one with no issue' do
+        it 'returns that one issue' do
+          expect(items.with_release('v2.0')).to contain_exactly(issue_3)
+        end
+
+        context 'when the milestone with no issue is added as a filter' do
+          it 'returns an empty list' do
+            expect(items.with_release('v2.0').with_milestone('m3')).to be_empty
+          end
+        end
+
+        context 'when the milestone with the issue is added as a filter' do
+          it 'returns this issue' do
+            expect(items.with_release('v2.0').with_milestone('m2')).to contain_exactly(issue_3)
+          end
+        end
+      end
+
+      context 'when an issue is tied to multiple milestones under the same release' do
+        it 'returns this issue only once' do
+          expect(items.with_release('v3.0')).to contain_exactly(issue_4)
+        end
+      end
+
+      context 'when there is no issue under a specific release' do
+        it 'returns no issue' do
+          expect(items.with_release('v4.0')).to be_empty
+        end
+      end
+
+      context 'when a non-existant release tag is passed in' do
+        it 'returns no issue' do
+          expect(items.with_release('v999.0')).to be_empty
+        end
+      end
+    end
+  end
 end