Merge branch 'master' of gitlab.com:gitlab-org/gitlab-ce into docs-pages-introdocs-pages-intro

11 files changed, 475 insertions, 51 deletions

diff --git a/spec/services/merge_requests/close_service_spec.rb b/spec/services/merge_requests/close_service_spec.rb
index 433ffbd97f0..706bcea8199 100644
--- a/spec/services/merge_requests/close_service_spec.rb
+++ b/spec/services/merge_requests/close_service_spec.rb
@@ -4,7 +4,7 @@ describe MergeRequests::CloseService do
   let(:user) { create(:user) }
   let(:user2) { create(:user) }
   let(:guest) { create(:user) }
-  let(:merge_request) { create(:merge_request, assignee: user2, author: create(:user)) }
+  let(:merge_request) { create(:merge_request, assignees: [user2], author: create(:user)) }
   let(:project) { merge_request.project }
   let!(:todo) { create(:todo, :assigned, user: user, project: project, target: merge_request, author: user2) }
 
diff --git a/spec/services/merge_requests/create_from_issue_service_spec.rb b/spec/services/merge_requests/create_from_issue_service_spec.rb
index 393299cce00..20bf1cbb8b6 100644
--- a/spec/services/merge_requests/create_from_issue_service_spec.rb
+++ b/spec/services/merge_requests/create_from_issue_service_spec.rb
@@ -118,7 +118,7 @@ describe MergeRequests::CreateFromIssueService do
 
       result = service.execute
 
-      expect(result[:merge_request].assignee).to eq(user)
+      expect(result[:merge_request].assignees).to eq([user])
     end
 
     context 'when ref branch is set' do
diff --git a/spec/services/merge_requests/create_service_spec.rb b/spec/services/merge_requests/create_service_spec.rb
index dc5d1cf2f04..30271e04c8e 100644
--- a/spec/services/merge_requests/create_service_spec.rb
+++ b/spec/services/merge_requests/create_service_spec.rb
@@ -32,7 +32,7 @@ describe MergeRequests::CreateService do
         expect(merge_request).to be_valid
         expect(merge_request.work_in_progress?).to be(false)
         expect(merge_request.title).to eq('Awesome merge_request')
-        expect(merge_request.assignee).to be_nil
+        expect(merge_request.assignees).to be_empty
         expect(merge_request.merge_params['force_remove_source_branch']).to eq('1')
       end
 
@@ -73,7 +73,7 @@ describe MergeRequests::CreateService do
               description: "well this is not done yet\n/wip",
               source_branch: 'feature',
               target_branch: 'master',
-              assignee: assignee
+              assignees: [assignee]
             }
           end
 
@@ -89,7 +89,7 @@ describe MergeRequests::CreateService do
               description: "well this is not done yet\n/wip",
               source_branch: 'feature',
               target_branch: 'master',
-              assignee: assignee
+              assignees: [assignee]
             }
           end
 
@@ -106,11 +106,11 @@ describe MergeRequests::CreateService do
             description: 'please fix',
             source_branch: 'feature',
             target_branch: 'master',
-            assignee: assignee
+            assignees: [assignee]
           }
         end
 
-        it { expect(merge_request.assignee).to eq assignee }
+        it { expect(merge_request.assignees).to eq([assignee]) }
 
         it 'creates a todo for new assignee' do
           attributes = {
@@ -301,7 +301,7 @@ describe MergeRequests::CreateService do
 
         let(:opts) do
           {
-            assignee_id: create(:user).id,
+            assignee_ids: create(:user).id,
             milestone_id: 1,
             title: 'Title',
             description: %(/assign @#{assignee.username}\n/milestone %"#{milestone.name}"),
@@ -317,7 +317,7 @@ describe MergeRequests::CreateService do
 
         it 'assigns and sets milestone to issuable from command' do
           expect(merge_request).to be_persisted
-          expect(merge_request.assignee).to eq(assignee)
+          expect(merge_request.assignees).to eq([assignee])
           expect(merge_request.milestone).to eq(milestone)
         end
       end
@@ -332,28 +332,28 @@ describe MergeRequests::CreateService do
         end
 
         it 'removes assignee_id when user id is invalid' do
-          opts = { title: 'Title', description: 'Description', assignee_id: -1 }
+          opts = { title: 'Title', description: 'Description', assignee_ids: [-1] }
 
           merge_request = described_class.new(project, user, opts).execute
 
-          expect(merge_request.assignee_id).to be_nil
+          expect(merge_request.assignee_ids).to be_empty
         end
 
         it 'removes assignee_id when user id is 0' do
-          opts = { title: 'Title', description: 'Description', assignee_id: 0 }
+          opts = { title: 'Title', description: 'Description', assignee_ids: [0] }
 
           merge_request = described_class.new(project, user, opts).execute
 
-          expect(merge_request.assignee_id).to be_nil
+          expect(merge_request.assignee_ids).to be_empty
         end
 
         it 'saves assignee when user id is valid' do
           project.add_maintainer(assignee)
-          opts = { title: 'Title', description: 'Description', assignee_id: assignee.id }
+          opts = { title: 'Title', description: 'Description', assignee_ids: [assignee.id] }
 
           merge_request = described_class.new(project, user, opts).execute
 
-          expect(merge_request.assignee).to eq(assignee)
+          expect(merge_request.assignees).to eq([assignee])
         end
 
         context 'when assignee is set' do
@@ -361,7 +361,7 @@ describe MergeRequests::CreateService do
             {
               title: 'Title',
               description: 'Description',
-              assignee_id: assignee.id,
+              assignee_ids: [assignee.id],
               source_branch: 'feature',
               target_branch: 'master'
             }
@@ -387,7 +387,7 @@ describe MergeRequests::CreateService do
           levels.each do |level|
             it "removes not authorized assignee when project is #{Gitlab::VisibilityLevel.level_name(level)}" do
               project.update(visibility_level: level)
-              opts = { title: 'Title', description: 'Description', assignee_id: assignee.id }
+              opts = { title: 'Title', description: 'Description', assignee_ids: [assignee.id] }
 
               merge_request = described_class.new(project, user, opts).execute
 
diff --git a/spec/services/merge_requests/ff_merge_service_spec.rb b/spec/services/merge_requests/ff_merge_service_spec.rb
index 1430e12a07e..a87d8b8752c 100644
--- a/spec/services/merge_requests/ff_merge_service_spec.rb
+++ b/spec/services/merge_requests/ff_merge_service_spec.rb
@@ -7,7 +7,7 @@ describe MergeRequests::FfMergeService do
     create(:merge_request,
            source_branch: 'flatten-dir',
            target_branch: 'improve/awesome',
-           assignee: user2,
+           assignees: [user2],
            author: create(:user))
   end
   let(:project) { merge_request.project }
diff --git a/spec/services/merge_requests/merge_service_spec.rb b/spec/services/merge_requests/merge_service_spec.rb
index 887ec17171e..b0b3273e3dc 100644
--- a/spec/services/merge_requests/merge_service_spec.rb
+++ b/spec/services/merge_requests/merge_service_spec.rb
@@ -3,7 +3,7 @@ require 'spec_helper'
 describe MergeRequests::MergeService do
   set(:user) { create(:user) }
   set(:user2) { create(:user) }
-  let(:merge_request) { create(:merge_request, :simple, author: user2, assignee: user2) }
+  let(:merge_request) { create(:merge_request, :simple, author: user2, assignees: [user2]) }
   let(:project) { merge_request.project }
 
   before do
@@ -111,7 +111,7 @@ describe MergeRequests::MergeService do
     end
 
     context 'closes related todos' do
-      let(:merge_request) { create(:merge_request, assignee: user, author: user) }
+      let(:merge_request) { create(:merge_request, assignees: [user], author: user) }
       let(:project) { merge_request.project }
       let(:service) { described_class.new(project, user, commit_message: 'Awesome message') }
       let!(:todo) do
diff --git a/spec/services/merge_requests/merge_to_ref_service_spec.rb b/spec/services/merge_requests/merge_to_ref_service_spec.rb
index a3b48abae26..24d09c1fd00 100644
--- a/spec/services/merge_requests/merge_to_ref_service_spec.rb
+++ b/spec/services/merge_requests/merge_to_ref_service_spec.rb
@@ -149,7 +149,7 @@ describe MergeRequests::MergeToRefService do
     end
 
     context 'does not close related todos' do
-      let(:merge_request) { create(:merge_request, assignee: user, author: user) }
+      let(:merge_request) { create(:merge_request, assignees: [user], author: user) }
       let(:project) { merge_request.project }
       let!(:todo) do
         create(:todo, :assigned,
diff --git a/spec/services/merge_requests/post_merge_service_spec.rb b/spec/services/merge_requests/post_merge_service_spec.rb
index 5ad6f5528f9..2cebefee5d6 100644
--- a/spec/services/merge_requests/post_merge_service_spec.rb
+++ b/spec/services/merge_requests/post_merge_service_spec.rb
@@ -2,7 +2,7 @@ require 'spec_helper'
 
 describe MergeRequests::PostMergeService do
   let(:user) { create(:user) }
-  let(:merge_request) { create(:merge_request, assignee: user) }
+  let(:merge_request) { create(:merge_request, assignees: [user]) }
   let(:project) { merge_request.project }
 
   before do
diff --git a/spec/services/merge_requests/push_options_handler_service_spec.rb b/spec/services/merge_requests/push_options_handler_service_spec.rb
new file mode 100644
index 00000000000..f7a39bb42d5
--- /dev/null
+++ b/spec/services/merge_requests/push_options_handler_service_spec.rb
@@ -0,0 +1,404 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe MergeRequests::PushOptionsHandlerService do
+  include ProjectForksHelper
+
+  let(:user) { create(:user) }
+  let(:project) { create(:project, :public, :repository) }
+  let(:forked_project) { fork_project(project, user, repository: true) }
+  let(:service) { described_class.new(project, user, changes, push_options) }
+  let(:source_branch) { 'fix' }
+  let(:target_branch) { 'feature' }
+  let(:new_branch_changes) { "#{Gitlab::Git::BLANK_SHA} 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/#{source_branch}" }
+  let(:existing_branch_changes) { "d14d6c0abdd253381df51a723d58691b2ee1ab08 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/#{source_branch}" }
+  let(:deleted_branch_changes) { "d14d6c0abdd253381df51a723d58691b2ee1ab08 #{Gitlab::Git::BLANK_SHA} refs/heads/#{source_branch}" }
+  let(:default_branch_changes) { "d14d6c0abdd253381df51a723d58691b2ee1ab08 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/#{project.default_branch}" }
+
+  before do
+    project.add_developer(user)
+  end
+
+  shared_examples_for 'a service that can create a merge request' do
+    subject(:last_mr) { MergeRequest.last }
+
+    it 'creates a merge request' do
+      expect { service.execute }.to change { MergeRequest.count }.by(1)
+    end
+
+    it 'sets the correct target branch' do
+      branch = push_options[:target] || project.default_branch
+
+      service.execute
+
+      expect(last_mr.target_branch).to eq(branch)
+    end
+
+    it 'assigns the MR to the user' do
+      service.execute
+
+      expect(last_mr.assignees).to contain_exactly(user)
+    end
+
+    context 'when project has been forked' do
+      let(:forked_project) { fork_project(project, user, repository: true) }
+      let(:service) { described_class.new(forked_project, user, changes, push_options) }
+
+      before do
+        allow(forked_project).to receive(:empty_repo?).and_return(false)
+      end
+
+      it 'sets the correct source project' do
+        service.execute
+
+        expect(last_mr.source_project).to eq(forked_project)
+      end
+
+      it 'sets the correct target project' do
+        service.execute
+
+        expect(last_mr.target_project).to eq(project)
+      end
+    end
+  end
+
+  shared_examples_for 'a service that can set the target of a merge request' do
+    subject(:last_mr) { MergeRequest.last }
+
+    it 'sets the target_branch' do
+      service.execute
+
+      expect(last_mr.target_branch).to eq(target_branch)
+    end
+  end
+
+  shared_examples_for 'a service that can set the merge request to merge when pipeline succeeds' do
+    subject(:last_mr) { MergeRequest.last }
+
+    it 'sets merge_when_pipeline_succeeds' do
+      service.execute
+
+      expect(last_mr.merge_when_pipeline_succeeds).to eq(true)
+    end
+
+    it 'sets merge_user to the user' do
+      service.execute
+
+      expect(last_mr.merge_user).to eq(user)
+    end
+  end
+
+  shared_examples_for 'a service that does not create a merge request' do
+    it do
+      expect { service.execute }.not_to change { MergeRequest.count }
+    end
+  end
+
+  shared_examples_for 'a service that does not update a merge request' do
+    it do
+      expect { service.execute }.not_to change { MergeRequest.maximum(:updated_at) }
+    end
+  end
+
+  shared_examples_for 'a service that does nothing' do
+    include_examples 'a service that does not create a merge request'
+    include_examples 'a service that does not update a merge request'
+  end
+
+  describe '`create` push option' do
+    let(:push_options) { { create: true } }
+
+    context 'with a new branch' do
+      let(:changes) { new_branch_changes }
+
+      it_behaves_like 'a service that can create a merge request'
+    end
+
+    context 'with an existing branch but no open MR' do
+      let(:changes) { existing_branch_changes }
+
+      it_behaves_like 'a service that can create a merge request'
+    end
+
+    context 'with an existing branch that has a merge request open' do
+      let(:changes) { existing_branch_changes }
+      let!(:merge_request) { create(:merge_request, source_project: project, source_branch: source_branch)}
+
+      it_behaves_like 'a service that does not create a merge request'
+    end
+
+    context 'with a deleted branch' do
+      let(:changes) { deleted_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+
+    context 'with the project default branch' do
+      let(:changes) { default_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+  end
+
+  describe '`merge_when_pipeline_succeeds` push option' do
+    let(:push_options) { { merge_when_pipeline_succeeds: true } }
+
+    context 'with a new branch' do
+      let(:changes) { new_branch_changes }
+
+      it_behaves_like 'a service that does not create a merge request'
+
+      it 'adds an error to the service' do
+        error = "A merge_request.create push option is required to create a merge request for branch #{source_branch}"
+
+        service.execute
+
+        expect(service.errors).to include(error)
+      end
+
+      context 'when coupled with the `create` push option' do
+        let(:push_options) { { create: true, merge_when_pipeline_succeeds: true } }
+
+        it_behaves_like 'a service that can create a merge request'
+        it_behaves_like 'a service that can set the merge request to merge when pipeline succeeds'
+      end
+    end
+
+    context 'with an existing branch but no open MR' do
+      let(:changes) { existing_branch_changes }
+
+      it_behaves_like 'a service that does not create a merge request'
+
+      it 'adds an error to the service' do
+        error = "A merge_request.create push option is required to create a merge request for branch #{source_branch}"
+
+        service.execute
+
+        expect(service.errors).to include(error)
+      end
+
+      context 'when coupled with the `create` push option' do
+        let(:push_options) { { create: true, merge_when_pipeline_succeeds: true } }
+
+        it_behaves_like 'a service that can create a merge request'
+        it_behaves_like 'a service that can set the merge request to merge when pipeline succeeds'
+      end
+    end
+
+    context 'with an existing branch that has a merge request open' do
+      let(:changes) { existing_branch_changes }
+      let!(:merge_request) { create(:merge_request, source_project: project, source_branch: source_branch)}
+
+      it_behaves_like 'a service that does not create a merge request'
+      it_behaves_like 'a service that can set the merge request to merge when pipeline succeeds'
+    end
+
+    context 'with a deleted branch' do
+      let(:changes) { deleted_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+
+    context 'with the project default branch' do
+      let(:changes) { default_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+  end
+
+  describe '`target` push option' do
+    let(:push_options) { { target: target_branch } }
+
+    context 'with a new branch' do
+      let(:changes) { new_branch_changes }
+
+      it_behaves_like 'a service that does not create a merge request'
+
+      it 'adds an error to the service' do
+        error = "A merge_request.create push option is required to create a merge request for branch #{source_branch}"
+
+        service.execute
+
+        expect(service.errors).to include(error)
+      end
+
+      context 'when coupled with the `create` push option' do
+        let(:push_options) { { create: true, target: target_branch } }
+
+        it_behaves_like 'a service that can create a merge request'
+        it_behaves_like 'a service that can set the target of a merge request'
+      end
+    end
+
+    context 'with an existing branch but no open MR' do
+      let(:changes) { existing_branch_changes }
+
+      it_behaves_like 'a service that does not create a merge request'
+
+      it 'adds an error to the service' do
+        error = "A merge_request.create push option is required to create a merge request for branch #{source_branch}"
+
+        service.execute
+
+        expect(service.errors).to include(error)
+      end
+
+      context 'when coupled with the `create` push option' do
+        let(:push_options) { { create: true, target: target_branch } }
+
+        it_behaves_like 'a service that can create a merge request'
+        it_behaves_like 'a service that can set the target of a merge request'
+      end
+    end
+
+    context 'with an existing branch that has a merge request open' do
+      let(:changes) { existing_branch_changes }
+      let!(:merge_request) { create(:merge_request, source_project: project, source_branch: source_branch)}
+
+      it_behaves_like 'a service that does not create a merge request'
+      it_behaves_like 'a service that can set the target of a merge request'
+    end
+
+    context 'with a deleted branch' do
+      let(:changes) { deleted_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+
+    context 'with the project default branch' do
+      let(:changes) { default_branch_changes }
+
+      it_behaves_like 'a service that does nothing'
+    end
+  end
+
+  describe 'multiple pushed branches' do
+    let(:push_options) { { create: true } }
+    let(:changes) do
+      [
+        new_branch_changes,
+        "#{Gitlab::Git::BLANK_SHA} 570e7b2abdd848b95f2f578043fc23bd6f6fd24d refs/heads/feature_conflict"
+      ]
+    end
+
+    it 'creates a merge request per branch' do
+      expect { service.execute }.to change { MergeRequest.count }.by(2)
+    end
+
+    context 'when there are too many pushed branches' do
+      let(:limit) { MergeRequests::PushOptionsHandlerService::LIMIT }
+      let(:changes) do
+        TestEnv::BRANCH_SHA.to_a[0..limit].map do |x|
+          "#{Gitlab::Git::BLANK_SHA} #{x.first} refs/heads/#{x.last}"
+        end
+      end
+
+      it 'records an error' do
+        service.execute
+
+        expect(service.errors).to eq(["Too many branches pushed (#{limit + 1} were pushed, limit is #{limit})"])
+      end
+    end
+  end
+
+  describe 'no push options' do
+    let(:push_options) { {} }
+    let(:changes) { new_branch_changes }
+
+    it_behaves_like 'a service that does nothing'
+  end
+
+  describe 'no user' do
+    let(:user) { nil }
+    let(:push_options) { { create: true } }
+    let(:changes) { new_branch_changes }
+
+    it 'records an error' do
+      service.execute
+
+      expect(service.errors).to eq(['User is required'])
+    end
+  end
+
+  describe 'unauthorized user' do
+    let(:push_options) { { create: true } }
+    let(:changes) { new_branch_changes }
+
+    it 'records an error' do
+      Members::DestroyService.new(user).execute(ProjectMember.find_by!(user_id: user.id))
+
+      service.execute
+
+      expect(service.errors).to eq(['User access was denied'])
+    end
+  end
+
+  describe 'handling unexpected exceptions' do
+    let(:push_options) { { create: true } }
+    let(:changes) { new_branch_changes }
+    let(:exception) { StandardError.new('My standard error') }
+
+    def run_service_with_exception
+      allow_any_instance_of(
+        MergeRequests::BuildService
+      ).to receive(:execute).and_raise(exception)
+
+      service.execute
+    end
+
+    it 'records an error' do
+      run_service_with_exception
+
+      expect(service.errors).to eq(['An unknown error occurred'])
+    end
+
+    it 'writes to Gitlab::AppLogger' do
+      expect(Gitlab::AppLogger).to receive(:error).with(exception)
+
+      run_service_with_exception
+    end
+  end
+
+  describe 'when target is not a valid branch name' do
+    let(:push_options) { { create: true, target: 'my-branch' } }
+    let(:changes) { new_branch_changes }
+
+    it 'records an error' do
+      service.execute
+
+      expect(service.errors).to eq(['Branch my-branch does not exist'])
+    end
+  end
+
+  describe 'when MRs are not enabled' do
+    let(:push_options) { { create: true } }
+    let(:changes) { new_branch_changes }
+
+    it 'records an error' do
+      expect(project).to receive(:merge_requests_enabled?).and_return(false)
+
+      service.execute
+
+      expect(service.errors).to eq(["Merge requests are not enabled for project #{project.full_path}"])
+    end
+  end
+
+  describe 'when MR has ActiveRecord errors' do
+    let(:push_options) { { create: true } }
+    let(:changes) { new_branch_changes }
+
+    it 'adds the error to its errors property' do
+      invalid_merge_request = MergeRequest.new
+      invalid_merge_request.errors.add(:base, 'my error')
+
+      expect_any_instance_of(
+        MergeRequests::CreateService
+      ).to receive(:execute).and_return(invalid_merge_request)
+
+      service.execute
+
+      expect(service.errors).to eq(['my error'])
+    end
+  end
+end
diff --git a/spec/services/merge_requests/refresh_service_spec.rb b/spec/services/merge_requests/refresh_service_spec.rb
index bd10523bc94..5ed06df7072 100644
--- a/spec/services/merge_requests/refresh_service_spec.rb
+++ b/spec/services/merge_requests/refresh_service_spec.rb
@@ -146,7 +146,10 @@ describe MergeRequests::RefreshService do
         stub_ci_pipeline_yaml_file(YAML.dump(config))
       end
 
-      subject { service.new(@project, @user).execute(@oldrev, @newrev, 'refs/heads/master') }
+      subject { service.new(project, @user).execute(@oldrev, @newrev, ref) }
+
+      let(:ref) { 'refs/heads/master' }
+      let(:project) { @project }
 
       context "when .gitlab-ci.yml has merge_requests keywords" do
         let(:config) do
@@ -162,14 +165,17 @@ describe MergeRequests::RefreshService do
         it 'create detached merge request pipeline with commits' do
           expect { subject }
             .to change { @merge_request.merge_request_pipelines.count }.by(1)
-            .and change { @fork_merge_request.merge_request_pipelines.count }.by(1)
             .and change { @another_merge_request.merge_request_pipelines.count }.by(0)
 
           expect(@merge_request.has_commits?).to be_truthy
-          expect(@fork_merge_request.has_commits?).to be_truthy
           expect(@another_merge_request.has_commits?).to be_falsy
         end
 
+        it 'does not create detached merge request pipeline for forked project' do
+          expect { subject }
+            .not_to change { @fork_merge_request.merge_request_pipelines.count }
+        end
+
         it 'create detached merge request pipeline for non-fork merge request' do
           subject
 
@@ -177,11 +183,25 @@ describe MergeRequests::RefreshService do
             .to be_detached_merge_request_pipeline
         end
 
-        it 'create legacy detached merge request pipeline for fork merge request' do
-          subject
+        context 'when service is hooked by target branch' do
+          let(:ref) { 'refs/heads/feature' }
 
-          expect(@fork_merge_request.merge_request_pipelines.first)
-            .to be_legacy_detached_merge_request_pipeline
+          it 'does not create detached merge request pipeline' do
+            expect { subject }
+              .not_to change { @merge_request.merge_request_pipelines.count }
+          end
+        end
+
+        context 'when service runs on forked project' do
+          let(:project) { @fork_project }
+
+          it 'creates legacy detached merge request pipeline for fork merge request' do
+            expect { subject }
+              .to change { @fork_merge_request.merge_request_pipelines.count }.by(1)
+
+            expect(@fork_merge_request.merge_request_pipelines.first)
+              .to be_legacy_detached_merge_request_pipeline
+          end
         end
 
         context 'when ci_use_merge_request_ref feature flag is false' do
diff --git a/spec/services/merge_requests/reopen_service_spec.rb b/spec/services/merge_requests/reopen_service_spec.rb
index 21e71509ed6..8b6db1ce33e 100644
--- a/spec/services/merge_requests/reopen_service_spec.rb
+++ b/spec/services/merge_requests/reopen_service_spec.rb
@@ -4,7 +4,7 @@ describe MergeRequests::ReopenService do
   let(:user) { create(:user) }
   let(:user2) { create(:user) }
   let(:guest) { create(:user) }
-  let(:merge_request) { create(:merge_request, :closed, assignee: user2, author: create(:user)) }
+  let(:merge_request) { create(:merge_request, :closed, assignees: [user2], author: create(:user)) }
   let(:project) { merge_request.project }
 
   before do
diff --git a/spec/services/merge_requests/update_service_spec.rb b/spec/services/merge_requests/update_service_spec.rb
index 8e367db031c..0525899ebfa 100644
--- a/spec/services/merge_requests/update_service_spec.rb
+++ b/spec/services/merge_requests/update_service_spec.rb
@@ -13,7 +13,7 @@ describe MergeRequests::UpdateService, :mailer do
   let(:merge_request) do
     create(:merge_request, :simple, title: 'Old title',
                                     description: "FYI #{user2.to_reference}",
-                                    assignee_id: user3.id,
+                                    assignee_ids: [user3.id],
                                     source_project: project,
                                     author: create(:user))
   end
@@ -48,7 +48,7 @@ describe MergeRequests::UpdateService, :mailer do
         {
           title: 'New title',
           description: 'Also please fix',
-          assignee_id: user2.id,
+          assignee_ids: [user.id],
           state_event: 'close',
           label_ids: [label.id],
           target_branch: 'target',
@@ -71,7 +71,7 @@ describe MergeRequests::UpdateService, :mailer do
       it 'matches base expectations' do
         expect(@merge_request).to be_valid
         expect(@merge_request.title).to eq('New title')
-        expect(@merge_request.assignee).to eq(user2)
+        expect(@merge_request.assignees).to match_array([user])
         expect(@merge_request).to be_closed
         expect(@merge_request.labels.count).to eq(1)
         expect(@merge_request.labels.first.title).to eq(label.name)
@@ -106,7 +106,7 @@ describe MergeRequests::UpdateService, :mailer do
         note = find_note('assigned to')
 
         expect(note).not_to be_nil
-        expect(note.note).to include "assigned to #{user2.to_reference}"
+        expect(note.note).to include "assigned to #{user.to_reference} and unassigned #{user3.to_reference}"
       end
 
       it 'creates a resource label event' do
@@ -293,7 +293,7 @@ describe MergeRequests::UpdateService, :mailer do
 
       context 'when is reassigned' do
         before do
-          update_merge_request({ assignee: user2 })
+          update_merge_request({ assignee_ids: [user2.id] })
         end
 
         it 'marks previous assignee pending todos as done' do
@@ -387,7 +387,7 @@ describe MergeRequests::UpdateService, :mailer do
 
       context 'when the assignee changes' do
         it 'updates open merge request counter for assignees when merge request is reassigned' do
-          update_merge_request(assignee_id: user2.id)
+          update_merge_request(assignee_ids: [user2.id])
 
           expect(user3.assigned_open_merge_requests_count).to eq 0
           expect(user2.assigned_open_merge_requests_count).to eq 1
@@ -541,36 +541,36 @@ describe MergeRequests::UpdateService, :mailer do
       end
     end
 
-    context 'updating asssignee_id' do
+    context 'updating asssignee_ids' do
       it 'does not update assignee when assignee_id is invalid' do
-        merge_request.update(assignee_id: user.id)
+        merge_request.update(assignee_ids: [user.id])
 
-        update_merge_request(assignee_id: -1)
+        update_merge_request(assignee_ids: [-1])
 
-        expect(merge_request.reload.assignee).to eq(user)
+        expect(merge_request.reload.assignees).to eq([user])
       end
 
       it 'unassigns assignee when user id is 0' do
-        merge_request.update(assignee_id: user.id)
+        merge_request.update(assignee_ids: [user.id])
 
-        update_merge_request(assignee_id: 0)
+        update_merge_request(assignee_ids: [0])
 
-        expect(merge_request.assignee_id).to be_nil
+        expect(merge_request.assignee_ids).to be_empty
       end
 
       it 'saves assignee when user id is valid' do
-        update_merge_request(assignee_id: user.id)
+        update_merge_request(assignee_ids: [user.id])
 
-        expect(merge_request.assignee_id).to eq(user.id)
+        expect(merge_request.assignee_ids).to eq([user.id])
       end
 
       it 'does not update assignee_id when user cannot read issue' do
-        non_member        = create(:user)
-        original_assignee = merge_request.assignee
+        non_member = create(:user)
+        original_assignees = merge_request.assignees
 
-        update_merge_request(assignee_id: non_member.id)
+        update_merge_request(assignee_ids: [non_member.id])
 
-        expect(merge_request.assignee_id).to eq(original_assignee.id)
+        expect(merge_request.reload.assignees).to eq(original_assignees)
       end
 
       context "when issuable feature is private" do
@@ -583,7 +583,7 @@ describe MergeRequests::UpdateService, :mailer do
             feature_visibility_attr = :"#{merge_request.model_name.plural}_access_level"
             project.project_feature.update_attribute(feature_visibility_attr, ProjectFeature::PRIVATE)
 
-            expect { update_merge_request(assignee_id: assignee) }.not_to change { merge_request.assignee }
+            expect { update_merge_request(assignee_ids: [assignee]) }.not_to change { merge_request.reload.assignees }
           end
         end
       end
@@ -619,7 +619,7 @@ describe MergeRequests::UpdateService, :mailer do
       end
 
       it 'is allowed by a user that can push to the source and can update the merge request' do
-        merge_request.update!(assignee: user)
+        merge_request.update!(assignees: [user])
         source_project.add_developer(user)
 
         update_merge_request(allow_collaboration: true, title: 'Updated title')