1 files changed, 106 insertions, 0 deletions
diff --git a/spec/requests/api/graphql/mutations/merge_requests/set_reviewers_spec.rb b/spec/requests/api/graphql/mutations/merge_requests/set_reviewers_spec.rb
new file mode 100644
index 00000000000..be786256ef2
--- /dev/null
+++ b/spec/requests/api/graphql/mutations/merge_requests/set_reviewers_spec.rb
@@ -0,0 +1,106 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'Setting reviewers of a merge request', :assume_throttled do
+  include GraphqlHelpers
+
+  let_it_be(:project) { create(:project, :repository) }
+  let_it_be(:current_user) { create(:user, developer_projects: [project]) }
+  let_it_be(:reviewer) { create(:user) }
+  let_it_be(:reviewer2) { create(:user) }
+  let_it_be_with_reload(:merge_request) { create(:merge_request, source_project: project) }
+
+  let(:input) { { reviewer_usernames: [reviewer.username] } }
+  let(:expected_result) do
+    [{ 'username' => reviewer.username }]
+  end
+
+  let(:mutation) do
+    variables = {
+      project_path: project.full_path,
+      iid: merge_request.iid.to_s
+    }
+    graphql_mutation(:merge_request_set_reviewers, variables.merge(input),
+                     <<-QL.strip_heredoc
+                       clientMutationId
+                       errors
+                       mergeRequest {
+                         id
+                         reviewers {
+                           nodes {
+                             username
+                           }
+                         }
+                       }
+    QL
+    )
+  end
+
+  def mutation_response
+    graphql_mutation_response(:merge_request_set_reviewers)
+  end
+
+  def mutation_reviewer_nodes
+    mutation_response['mergeRequest']['reviewers']['nodes']
+  end
+
+  def run_mutation!
+    post_graphql_mutation(mutation, current_user: current_user)
+  end
+
+  before do
+    project.add_developer(reviewer)
+    project.add_developer(reviewer2)
+
+    merge_request.update!(reviewers: [])
+  end
+
+  it 'returns an error if the user is not allowed to update the merge request' do
+    post_graphql_mutation(mutation, current_user: create(:user))
+
+    expect(graphql_errors).not_to be_empty
+  end
+
+  context 'when the current user does not have permission to add reviewers' do
+    let(:current_user) { create(:user) }
+
+    it 'does not change the reviewers' do
+      project.add_guest(current_user)
+
+      expect { run_mutation! }.not_to change { merge_request.reset.reviewers.pluck(:id) }
+
+      expect(graphql_errors).not_to be_empty
+    end
+  end
+
+  context 'with reviewers already assigned' do
+    before do
+      merge_request.reviewers = [reviewer2]
+      merge_request.save!
+    end
+
+    it 'replaces the reviewer' do
+      run_mutation!
+
+      expect(response).to have_gitlab_http_status(:success)
+      expect(mutation_reviewer_nodes).to match_array(expected_result)
+    end
+  end
+
+  context 'when passing an empty list of reviewers' do
+    let(:input) { { reviewer_usernames: [] } }
+
+    before do
+      merge_request.reviewers = [reviewer2]
+      merge_request.save!
+    end
+
+    it 'removes reviewer' do
+      run_mutation!
+
+      expect(response).to have_gitlab_http_status(:success)
+      expect(mutation_reviewer_nodes).to eq([])
+    end
+  end
+end