diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index 135117926be..a3ceb76845e 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -33,7 +33,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
 
   def show
     close_merge_request_if_no_source_project
-    @merge_request.check_mergeability
+    mark_merge_request_mergeable
 
     respond_to do |format|
       format.html do
@@ -251,6 +251,10 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
     @merge_request.has_no_commits? && !@merge_request.target_branch_exists?
   end
 
+  def mark_merge_request_mergeable
+    @merge_request.check_if_can_be_merged
+  end
+
   def merge!
     # Disable the CI check if auto_merge_strategy is specified since we have
     # to wait until CI completes to know
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 4fcaac75655..7481f1939ad 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -725,16 +725,19 @@ class MergeRequest < ApplicationRecord
 
     MergeRequests::ReloadDiffsService.new(self, current_user).execute
   end
-
-  def check_mergeability
-    MergeRequests::MergeabilityCheckService.new(self).execute
-  end
   # rubocop: enable CodeReuse/ServiceClass
 
-  # Returns boolean indicating the merge_status should be rechecked in order to
-  # switch to either can_be_merged or cannot_be_merged.
-  def recheck_merge_status?
-    self.class.state_machines[:merge_status].check_state?(merge_status)
+  def check_if_can_be_merged
+    return unless self.class.state_machines[:merge_status].check_state?(merge_status) && Gitlab::Database.read_write?
+
+    can_be_merged =
+      !broken? && project.repository.can_be_merged?(diff_head_sha, target_branch)
+
+    if can_be_merged
+      mark_as_mergeable
+    else
+      mark_as_unmergeable
+    end
   end
 
   def merge_event
@@ -760,7 +763,7 @@ class MergeRequest < ApplicationRecord
   def mergeable?(skip_ci_check: false)
     return false unless mergeable_state?(skip_ci_check: skip_ci_check)
 
-    check_mergeability
+    check_if_can_be_merged
 
     can_be_merged? && !should_be_rebased?
   end
@@ -775,6 +778,15 @@ class MergeRequest < ApplicationRecord
     true
   end
 
+  def mergeable_to_ref?
+    return false unless mergeable_state?(skip_ci_check: true, skip_discussions_check: true)
+
+    # Given the `merge_ref_path` will have the same
+    # state the `target_branch` would have. Ideally
+    # we need to check if it can be merged to it.
+    project.repository.can_be_merged?(diff_head_sha, target_branch)
+  end
+
   def ff_merge_possible?
     project.repository.ancestor?(target_branch_sha, diff_head_sha)
   end
@@ -1087,12 +1099,6 @@ class MergeRequest < ApplicationRecord
     target_project.repository.fetch_source_branch!(source_project.repository, source_branch, ref_path)
   end
 
-  # Returns the current merge-ref HEAD commit.
-  #
-  def merge_ref_head
-    project.repository.commit(merge_ref_path)
-  end
-
   def ref_path
     "refs/#{Repository::REF_MERGE_REQUEST}/#{iid}/head"
   end
diff --git a/app/services/merge_requests/merge_to_ref_service.rb b/app/services/merge_requests/merge_to_ref_service.rb
index 8670b9ccf3d..87147d90c32 100644
--- a/app/services/merge_requests/merge_to_ref_service.rb
+++ b/app/services/merge_requests/merge_to_ref_service.rb
@@ -20,14 +20,20 @@ module MergeRequests
 
       raise_error('Conflicts detected during merge') unless commit_id
 
-      success(commit_id: commit_id)
-    rescue MergeError, ArgumentError => error
+      commit = project.commit(commit_id)
+      target_id, source_id = commit.parent_ids
+
+      success(commit_id: commit.id,
+              target_id: target_id,
+              source_id: source_id)
+    rescue MergeError => error
       error(error.message)
     end
 
     private
 
     def validate!
+      authorization_check!
       error_check!
     end
 
@@ -37,13 +43,21 @@ module MergeRequests
       error =
         if !hooks_validation_pass?(merge_request)
           hooks_validation_error(merge_request)
-        elsif source.blank?
+        elsif !@merge_request.mergeable_to_ref?
+          "Merge request is not mergeable to #{target_ref}"
+        elsif !source
           'No source for merge'
         end
 
       raise_error(error) if error
     end
 
+    def authorization_check!
+      unless Ability.allowed?(current_user, :admin_merge_request, project)
+        raise_error("You are not allowed to merge to this ref")
+      end
+    end
+
     def target_ref
       merge_request.merge_ref_path
     end
diff --git a/app/services/merge_requests/mergeability_check_service.rb b/app/services/merge_requests/mergeability_check_service.rb
deleted file mode 100644
index ef833774e65..00000000000
--- a/app/services/merge_requests/mergeability_check_service.rb
+++ /dev/null
@@ -1,82 +0,0 @@
-# frozen_string_literal: true
-
-module MergeRequests
-  class MergeabilityCheckService < ::BaseService
-    include Gitlab::Utils::StrongMemoize
-
-    delegate :project, to: :@merge_request
-    delegate :repository, to: :project
-
-    def initialize(merge_request)
-      @merge_request = merge_request
-    end
-
-    # Updates the MR merge_status. Whenever it switches to a can_be_merged state,
-    # the merge-ref is refreshed.
-    #
-    # Returns a ServiceResponse indicating merge_status is/became can_be_merged
-    # and the merge-ref is synced. Success in case of being/becoming mergeable,
-    # error otherwise.
-    def execute
-      return ServiceResponse.error(message: 'Invalid argument') unless merge_request
-      return ServiceResponse.error(message: 'Unsupported operation') if Gitlab::Database.read_only?
-
-      update_merge_status
-
-      unless merge_request.can_be_merged?
-        return ServiceResponse.error(message: 'Merge request is not mergeable')
-      end
-
-      unless payload.fetch(:merge_ref_head)
-        return ServiceResponse.error(message: 'Merge ref was not found')
-      end
-
-      ServiceResponse.success(payload: payload)
-    end
-
-    private
-
-    attr_reader :merge_request
-
-    def payload
-      strong_memoize(:payload) do
-        {
-          merge_ref_head: merge_ref_head_payload
-        }
-      end
-    end
-
-    def merge_ref_head_payload
-      commit = merge_request.merge_ref_head
-
-      return unless commit
-
-      target_id, source_id = commit.parent_ids
-
-      {
-        commit_id: commit.id,
-        source_id: source_id,
-        target_id: target_id
-      }
-    end
-
-    def update_merge_status
-      return unless merge_request.recheck_merge_status?
-
-      if can_git_merge?
-        merge_to_ref && merge_request.mark_as_mergeable
-      else
-        merge_request.mark_as_unmergeable
-      end
-    end
-
-    def can_git_merge?
-      !merge_request.broken? && repository.can_be_merged?(merge_request.diff_head_sha, merge_request.target_branch)
-    end
-
-    def merge_to_ref
-      result = MergeRequests::MergeToRefService.new(project, merge_request.author).execute(merge_request)
-      result[:status] == :success
-    end
-  end
-end
diff --git a/app/services/service_response.rb b/app/services/service_response.rb
index f3437ba16de..1de30e68d87 100644
--- a/app/services/service_response.rb
+++ b/app/services/service_response.rb
@@ -1,20 +1,19 @@
 # frozen_string_literal: true
 
 class ServiceResponse
-  def self.success(message: nil, payload: {})
-    new(status: :success, message: message, payload: payload)
+  def self.success(message: nil)
+    new(status: :success, message: message)
   end
 
-  def self.error(message:, payload: {}, http_status: nil)
-    new(status: :error, message: message, payload: payload, http_status: http_status)
+  def self.error(message:, http_status: nil)
+    new(status: :error, message: message, http_status: http_status)
   end
 
-  attr_reader :status, :message, :http_status, :payload
+  attr_reader :status, :message, :http_status
 
-  def initialize(status:, message: nil, payload: {}, http_status: nil)
+  def initialize(status:, message: nil, http_status: nil)
     self.status = status
     self.message = message
-    self.payload = payload
     self.http_status = http_status
   end
 
@@ -28,5 +27,5 @@ class ServiceResponse
 
   private
 
-  attr_writer :status, :message, :http_status, :payload
+  attr_writer :status, :message, :http_status
 end
diff --git a/changelogs/unreleased/osw-sync-merge-ref-upon-mergeability-check.yml b/changelogs/unreleased/osw-sync-merge-ref-upon-mergeability-check.yml
deleted file mode 100644
index 1f40089adb8..00000000000
--- a/changelogs/unreleased/osw-sync-merge-ref-upon-mergeability-check.yml
+++ /dev/null
@@ -1,5 +0,0 @@
----
-title: Sync merge ref upon mergeability check
-merge_request: 28513
-author:
-type: added
diff --git a/doc/api/merge_requests.md b/doc/api/merge_requests.md
index 96a956ad03a..dd7810c3403 100644
--- a/doc/api/merge_requests.md
+++ b/doc/api/merge_requests.md
@@ -1191,29 +1191,33 @@ Parameters:
 }
 ```
 
-## Returns the up to date merge-ref HEAD commit
+## Merge to default merge ref path
 
-Merge the changes between the merge request source and target branches into `refs/merge-requests/:iid/merge`
-ref, of the target project repository, if possible. This ref will have the state the target branch would have if
+Merge the changes between the merge request source and target branches into `refs/merge-requests/:iid/merge` 
+ref, of the target project repository. This ref will have the state the target branch would have if
 a regular merge action was taken.
 
-This is not a regular merge action given it doesn't change the merge request target branch state in any manner.
+This is not a regular merge action given it doesn't change the merge request state in any manner.
 
-This ref (`refs/merge-requests/:iid/merge`) isn't necessarily overwritten when submitting
-requests to this API, though it'll make sure the ref has the latest possible state.
+This ref (`refs/merge-requests/:iid/merge`) is **always** overwritten when submitting
+requests to this API, so none of its state is kept or used in the process.
 
-If the merge request has conflicts, is empty or already merged, you'll get a `400` and a descriptive error message.
+If the merge request has conflicts, is empty or already merged,
+you'll get a `400` and a descriptive error message. If you don't have permissions to do so, 
+you'll get a `403`.
 
-It returns the HEAD commit of `refs/merge-requests/:iid/merge` in the response body in case of `200`.
+It returns the HEAD commit of `refs/merge-requests/:iid/merge` in the response body in
+case of `200`.
 
 ```
-GET /projects/:id/merge_requests/:merge_request_iid/merge_ref
+PUT /projects/:id/merge_requests/:merge_request_iid/merge_to_ref
 ```
 
 Parameters:
 
 - `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
 - `merge_request_iid` (required)            - Internal ID of MR
+- `merge_commit_message` (optional)         - Custom merge commit message
 
 ```json
 {
diff --git a/lib/api/entities.rb b/lib/api/entities.rb
index f8b950cb55d..880b07d0a84 100644
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -701,7 +701,7 @@ module API
       # See https://gitlab.com/gitlab-org/gitlab-ce/issues/42344 for more
       # information.
       expose :merge_status do |merge_request|
-        merge_request.check_mergeability
+        merge_request.check_if_can_be_merged
         merge_request.merge_status
       end
       expose :diff_head_sha, as: :sha
diff --git a/lib/api/merge_requests.rb b/lib/api/merge_requests.rb
index 5bbf6df78b0..955624404f1 100644
--- a/lib/api/merge_requests.rb
+++ b/lib/api/merge_requests.rb
@@ -397,16 +397,28 @@ module API
         present merge_request, with: Entities::MergeRequest, current_user: current_user, project: user_project
       end
 
-      desc 'Returns the up to date merge-ref HEAD commit'
-      get ':id/merge_requests/:merge_request_iid/merge_ref' do
+      desc 'Merge a merge request to its default temporary merge ref path'
+      params do
+        optional :merge_commit_message, type: String, desc: 'Custom merge commit message'
+      end
+      put ':id/merge_requests/:merge_request_iid/merge_to_ref' do
         merge_request = find_project_merge_request(params[:merge_request_iid])
 
-        result = ::MergeRequests::MergeabilityCheckService.new(merge_request).execute
+        authorize! :admin_merge_request, user_project
 
-        if result.success?
-          present :commit_id, result.payload.dig(:merge_ref_head, :commit_id)
+        merge_params = {
+          commit_message: params[:merge_commit_message]
+        }
+
+        result = ::MergeRequests::MergeToRefService
+          .new(merge_request.target_project, current_user, merge_params)
+          .execute(merge_request)
+
+        if result[:status] == :success
+          present result.slice(:commit_id), 200
         else
-          render_api_error!(result.message, 400)
+          http_status = result[:http_status] || 400
+          render_api_error!(result[:message], http_status)
         end
       end
 
diff --git a/spec/models/merge_request_spec.rb b/spec/models/merge_request_spec.rb
index fc28c216b21..c6251326c22 100644
--- a/spec/models/merge_request_spec.rb
+++ b/spec/models/merge_request_spec.rb
@@ -1996,6 +1996,57 @@ describe MergeRequest do
     end
   end
 
+  describe '#check_if_can_be_merged' do
+    let(:project) { create(:project, only_allow_merge_if_pipeline_succeeds: true) }
+
+    shared_examples 'checking if can be merged' do
+      context 'when it is not broken and has no conflicts' do
+        before do
+          allow(subject).to receive(:broken?) { false }
+          allow(project.repository).to receive(:can_be_merged?).and_return(true)
+        end
+
+        it 'is marked as mergeable' do
+          expect { subject.check_if_can_be_merged }.to change { subject.merge_status }.to('can_be_merged')
+        end
+      end
+
+      context 'when broken' do
+        before do
+          allow(subject).to receive(:broken?) { true }
+          allow(project.repository).to receive(:can_be_merged?).and_return(false)
+        end
+
+        it 'becomes unmergeable' do
+          expect { subject.check_if_can_be_merged }.to change { subject.merge_status }.to('cannot_be_merged')
+        end
+      end
+
+      context 'when it has conflicts' do
+        before do
+          allow(subject).to receive(:broken?) { false }
+          allow(project.repository).to receive(:can_be_merged?).and_return(false)
+        end
+
+        it 'becomes unmergeable' do
+          expect { subject.check_if_can_be_merged }.to change { subject.merge_status }.to('cannot_be_merged')
+        end
+      end
+    end
+
+    context 'when merge_status is unchecked' do
+      subject { create(:merge_request, source_project: project, merge_status: :unchecked) }
+
+      it_behaves_like 'checking if can be merged'
+    end
+
+    context 'when merge_status is unchecked' do
+      subject { create(:merge_request, source_project: project, merge_status: :cannot_be_merged_recheck) }
+
+      it_behaves_like 'checking if can be merged'
+    end
+  end
+
   describe '#mergeable?' do
     let(:project) { create(:project) }
 
@@ -2009,7 +2060,7 @@ describe MergeRequest do
 
     it 'return true if #mergeable_state? is true and the MR #can_be_merged? is true' do
       allow(subject).to receive(:mergeable_state?) { true }
-      expect(subject).to receive(:check_mergeability)
+      expect(subject).to receive(:check_if_can_be_merged)
       expect(subject).to receive(:can_be_merged?) { true }
 
       expect(subject.mergeable?).to be_truthy
@@ -2023,7 +2074,7 @@ describe MergeRequest do
 
     it 'checks if merge request can be merged' do
       allow(subject).to receive(:mergeable_ci_state?) { true }
-      expect(subject).to receive(:check_mergeability)
+      expect(subject).to receive(:check_if_can_be_merged)
 
       subject.mergeable?
     end
@@ -3091,6 +3142,38 @@ describe MergeRequest do
     end
   end
 
+  describe '#mergeable_to_ref?' do
+    it 'returns true when merge request is mergeable' do
+      subject = create(:merge_request)
+
+      expect(subject.mergeable_to_ref?).to be(true)
+    end
+
+    it 'returns false when merge request is already merged' do
+      subject = create(:merge_request, :merged)
+
+      expect(subject.mergeable_to_ref?).to be(false)
+    end
+
+    it 'returns false when merge request is closed' do
+      subject = create(:merge_request, :closed)
+
+      expect(subject.mergeable_to_ref?).to be(false)
+    end
+
+    it 'returns false when merge request is work in progress' do
+      subject = create(:merge_request, title: 'WIP: The feature')
+
+      expect(subject.mergeable_to_ref?).to be(false)
+    end
+
+    it 'returns false when merge request has no commits' do
+      subject = create(:merge_request, source_branch: 'empty-branch', target_branch: 'master')
+
+      expect(subject.mergeable_to_ref?).to be(false)
+    end
+  end
+
   describe '#merge_participants' do
     it 'contains author' do
       expect(subject.merge_participants).to eq([subject.author])
diff --git a/spec/requests/api/merge_requests_spec.rb b/spec/requests/api/merge_requests_spec.rb
index 4cb4fcc890d..9f9180bc8c9 100644
--- a/spec/requests/api/merge_requests_spec.rb
+++ b/spec/requests/api/merge_requests_spec.rb
@@ -1546,65 +1546,52 @@ describe API::MergeRequests do
     end
   end
 
-  describe "GET /projects/:id/merge_requests/:merge_request_iid/merge_ref" do
-    before do
-      merge_request.mark_as_unchecked!
-    end
-
-    let(:merge_request_iid) { merge_request.iid }
-
+  describe "PUT /projects/:id/merge_requests/:merge_request_iid/merge_to_ref" do
+    let(:pipeline) { create(:ci_pipeline_without_jobs) }
     let(:url) do
-      "/projects/#{project.id}/merge_requests/#{merge_request_iid}/merge_ref"
+      "/projects/#{project.id}/merge_requests/#{merge_request.iid}/merge_to_ref"
     end
 
     it 'returns the generated ID from the merge service in case of success' do
-      get api(url, user)
+      put api(url, user), params: { merge_commit_message: 'Custom message' }
+
+      commit = project.commit(json_response['commit_id'])
 
       expect(response).to have_gitlab_http_status(200)
-      expect(json_response['commit_id']).to eq(merge_request.merge_ref_head.sha)
+      expect(json_response['commit_id']).to be_present
+      expect(commit.message).to eq('Custom message')
     end
 
     it "returns 400 if branch can't be merged" do
-      merge_request.update!(merge_status: 'cannot_be_merged')
+      merge_request.update!(state: 'merged')
 
-      get api(url, user)
+      put api(url, user)
 
       expect(response).to have_gitlab_http_status(400)
-      expect(json_response['message']).to eq('Merge request is not mergeable')
+      expect(json_response['message'])
+        .to eq("Merge request is not mergeable to #{merge_request.merge_ref_path}")
     end
 
-    context 'when user has no access to the MR' do
-      let(:project) { create(:project, :private) }
-      let(:merge_request) { create(:merge_request, source_project: project, target_project: project) }
+    it 'returns 403 if user has no permissions to merge to the ref' do
+      user2 = create(:user)
+      project.add_reporter(user2)
 
-      it 'returns 404' do
-        project.add_guest(user)
+      put api(url, user2)
 
-        get api(url, user)
-
-        expect(response).to have_gitlab_http_status(404)
-        expect(json_response['message']).to eq('404 Not found')
-      end
+      expect(response).to have_gitlab_http_status(403)
+      expect(json_response['message']).to eq('403 Forbidden')
     end
 
-    context 'when invalid merge request IID' do
-      let(:merge_request_iid) { '12345' }
+    it 'returns 404 for an invalid merge request IID' do
+      put api("/projects/#{project.id}/merge_requests/12345/merge_to_ref", user)
 
-      it 'returns 404' do
-        get api(url, user)
-
-        expect(response).to have_gitlab_http_status(404)
-      end
+      expect(response).to have_gitlab_http_status(404)
     end
 
-    context 'when merge request ID is used instead IID' do
-      let(:merge_request_iid) { merge_request.id }
+    it "returns 404 if the merge request id is used instead of iid" do
+      put api("/projects/#{project.id}/merge_requests/#{merge_request.id}/merge", user)
 
-      it 'returns 404' do
-        get api(url, user)
-
-        expect(response).to have_gitlab_http_status(404)
-      end
+      expect(response).to have_gitlab_http_status(404)
     end
   end
 
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 5d492e4b013..0ac23050caf 100644
--- a/spec/services/merge_requests/merge_to_ref_service_spec.rb
+++ b/spec/services/merge_requests/merge_to_ref_service_spec.rb
@@ -32,8 +32,10 @@ describe MergeRequests::MergeToRefService do
 
       expect(result[:status]).to eq(:success)
       expect(result[:commit_id]).to be_present
+      expect(result[:source_id]).to eq(merge_request.source_branch_sha)
+      expect(result[:target_id]).to eq(merge_request.target_branch_sha)
       expect(repository.ref_exists?(target_ref)).to be(true)
-      expect(ref_head.sha).to eq(result[:commit_id])
+      expect(ref_head.id).to eq(result[:commit_id])
     end
   end
 
@@ -70,6 +72,10 @@ describe MergeRequests::MergeToRefService do
   let(:merge_request) { create(:merge_request, :simple) }
   let(:project) { merge_request.project }
 
+  before do
+    project.add_maintainer(user)
+  end
+
   describe '#execute' do
     let(:service) do
       described_class.new(project, user, commit_message: 'Awesome message',
@@ -86,12 +92,6 @@ describe MergeRequests::MergeToRefService do
     it_behaves_like 'successfully evaluates pre-condition checks'
 
     context 'commit history comparison with regular MergeService' do
-      before do
-        # The merge service needs an authorized user while merge-to-ref
-        # doesn't.
-        project.add_maintainer(user)
-      end
-
       let(:merge_ref_service) do
         described_class.new(project, user, {})
       end
@@ -136,9 +136,9 @@ describe MergeRequests::MergeToRefService do
         let(:merge_method) { :merge }
 
         it 'returns error' do
-          allow(project).to receive_message_chain(:repository, :merge_to_ref) { nil }
+          allow(merge_request).to receive(:mergeable_to_ref?) { false }
 
-          error_message = 'Conflicts detected during merge'
+          error_message = "Merge request is not mergeable to #{merge_request.merge_ref_path}"
 
           result = service.execute(merge_request)
 
@@ -170,5 +170,28 @@ describe MergeRequests::MergeToRefService do
 
       it { expect(todo).not_to be_done }
     end
+
+    context 'when merge request is WIP state' do
+      it 'fails to merge' do
+        merge_request = create(:merge_request, title: 'WIP: The feature')
+
+        result = service.execute(merge_request)
+
+        expect(result[:status]).to eq(:error)
+        expect(result[:message]).to eq("Merge request is not mergeable to #{merge_request.merge_ref_path}")
+      end
+    end
+
+    it 'returns error when user has no authorization to admin the merge request' do
+      unauthorized_user = create(:user)
+      project.add_reporter(unauthorized_user)
+
+      service = described_class.new(project, unauthorized_user)
+
+      result = service.execute(merge_request)
+
+      expect(result[:status]).to eq(:error)
+      expect(result[:message]).to eq('You are not allowed to merge to this ref')
+    end
   end
 end
diff --git a/spec/services/merge_requests/mergeability_check_service_spec.rb b/spec/services/merge_requests/mergeability_check_service_spec.rb
deleted file mode 100644
index aa0485467ed..00000000000
--- a/spec/services/merge_requests/mergeability_check_service_spec.rb
+++ /dev/null
@@ -1,187 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe MergeRequests::MergeabilityCheckService do
-  shared_examples_for 'unmergeable merge request' do
-    it 'updates or keeps merge status as cannot_be_merged' do
-      subject
-
-      expect(merge_request.merge_status).to eq('cannot_be_merged')
-    end
-
-    it 'does not change the merge ref HEAD' do
-      expect { subject }.not_to change(merge_request, :merge_ref_head)
-    end
-
-    it 'returns ServiceResponse.error' do
-      result = subject
-
-      expect(result).to be_a(ServiceResponse)
-      expect(result).to be_error
-    end
-  end
-
-  shared_examples_for 'mergeable merge request' do
-    it 'updates or keeps merge status as can_be_merged' do
-      subject
-
-      expect(merge_request.merge_status).to eq('can_be_merged')
-    end
-
-    it 'updates the merge ref' do
-      expect { subject }.to change(merge_request, :merge_ref_head).from(nil)
-    end
-
-    it 'returns ServiceResponse.success' do
-      result = subject
-
-      expect(result).to be_a(ServiceResponse)
-      expect(result).to be_success
-    end
-
-    it 'ServiceResponse has merge_ref_head payload' do
-      result = subject
-
-      expect(result.payload.keys).to contain_exactly(:merge_ref_head)
-      expect(result.payload[:merge_ref_head].keys)
-        .to contain_exactly(:commit_id, :target_id, :source_id)
-    end
-  end
-
-  describe '#execute' do
-    let(:project) { create(:project, :repository) }
-    let(:merge_request) { create(:merge_request, merge_status: :unchecked, source_project: project, target_project: project) }
-    let(:repo) { project.repository }
-
-    subject { described_class.new(merge_request).execute }
-
-    before do
-      project.add_developer(merge_request.author)
-    end
-
-    it_behaves_like 'mergeable merge request'
-
-    context 'when multiple calls to the service' do
-      it 'returns success' do
-        subject
-        result = subject
-
-        expect(result).to be_a(ServiceResponse)
-        expect(result.success?).to be(true)
-      end
-
-      it 'second call does not change the merge-ref' do
-        expect { subject }.to change(merge_request, :merge_ref_head).from(nil)
-        expect { subject }.not_to change(merge_request, :merge_ref_head)
-      end
-    end
-
-    context 'when broken' do
-      before do
-        allow(merge_request).to receive(:broken?) { true }
-        allow(project.repository).to receive(:can_be_merged?) { false }
-      end
-
-      it_behaves_like 'unmergeable merge request'
-
-      it 'returns ServiceResponse.error' do
-        result = subject
-
-        expect(result).to be_a(ServiceResponse)
-        expect(result.error?).to be(true)
-        expect(result.message).to eq('Merge request is not mergeable')
-      end
-    end
-
-    context 'when it has conflicts' do
-      before do
-        allow(merge_request).to receive(:broken?) { false }
-        allow(project.repository).to receive(:can_be_merged?) { false }
-      end
-
-      it_behaves_like 'unmergeable merge request'
-
-      it 'returns ServiceResponse.error' do
-        result = subject
-
-        expect(result).to be_a(ServiceResponse)
-        expect(result.error?).to be(true)
-        expect(result.message).to eq('Merge request is not mergeable')
-      end
-    end
-
-    context 'when MR cannot be merged and has no merge ref' do
-      before do
-        merge_request.mark_as_unmergeable!
-      end
-
-      it_behaves_like 'unmergeable merge request'
-
-      it 'returns ServiceResponse.error' do
-        result = subject
-
-        expect(result).to be_a(ServiceResponse)
-        expect(result.error?).to be(true)
-        expect(result.message).to eq('Merge request is not mergeable')
-      end
-    end
-
-    context 'when MR cannot be merged and has outdated merge ref' do
-      before do
-        MergeRequests::MergeToRefService.new(project, merge_request.author).execute(merge_request)
-        merge_request.mark_as_unmergeable!
-      end
-
-      it_behaves_like 'unmergeable merge request'
-
-      it 'returns ServiceResponse.error' do
-        result = subject
-
-        expect(result).to be_a(ServiceResponse)
-        expect(result.error?).to be(true)
-        expect(result.message).to eq('Merge request is not mergeable')
-      end
-    end
-
-    context 'when merge request is not given' do
-      subject { described_class.new(nil).execute }
-
-      it 'returns ServiceResponse.error' do
-        result = subject
-
-        expect(result).to be_a(ServiceResponse)
-        expect(result.message).to eq('Invalid argument')
-      end
-    end
-
-    context 'when read only DB' do
-      it 'returns ServiceResponse.error' do
-        allow(Gitlab::Database).to receive(:read_only?) { true }
-
-        result = subject
-
-        expect(result).to be_a(ServiceResponse)
-        expect(result.message).to eq('Unsupported operation')
-      end
-    end
-
-    context 'when MR is mergeable but merge-ref does not exists' do
-      before do
-        merge_request.mark_as_mergeable!
-      end
-
-      it 'keeps merge status as can_be_merged' do
-        expect { subject }.not_to change(merge_request, :merge_status).from('can_be_merged')
-      end
-
-      it 'returns ServiceResponse.error' do
-        result = subject
-
-        expect(result).to be_a(ServiceResponse)
-        expect(result.error?).to be(true)
-        expect(result.message).to eq('Merge ref was not found')
-      end
-    end
-  end
-end
diff --git a/spec/services/service_response_spec.rb b/spec/services/service_response_spec.rb
index e790d272e61..30bd4d6820b 100644
--- a/spec/services/service_response_spec.rb
+++ b/spec/services/service_response_spec.rb
@@ -16,13 +16,6 @@ describe ServiceResponse do
       expect(response).to be_success
       expect(response.message).to eq('Good orange')
     end
-
-    it 'creates a successful response with payload' do
-      response = described_class.success(payload: { good: 'orange' })
-
-      expect(response).to be_success
-      expect(response.payload).to eq(good: 'orange')
-    end
   end
 
   describe '.error' do
@@ -40,15 +33,6 @@ describe ServiceResponse do
       expect(response.message).to eq('Bad apple')
       expect(response.http_status).to eq(400)
     end
-
-    it 'creates a failed response with payload' do
-      response = described_class.error(message: 'Bad apple',
-                                       payload: { bad: 'apple' })
-
-      expect(response).to be_error
-      expect(response.message).to eq('Bad apple')
-      expect(response.payload).to eq(bad: 'apple')
-    end
   end
 
   describe '#success?' do