1 files changed, 16 insertions, 0 deletions
diff --git a/spec/requests/api/graphql/mutations/merge_requests/set_milestone_spec.rb b/spec/requests/api/graphql/mutations/merge_requests/set_milestone_spec.rb
index 3907ebad9ce..1898ee5a62d 100644
--- a/spec/requests/api/graphql/mutations/merge_requests/set_milestone_spec.rb
+++ b/spec/requests/api/graphql/mutations/merge_requests/set_milestone_spec.rb
@@ -63,4 +63,20 @@ RSpec.describe 'Setting milestone of a merge request', feature_category: :code_r
       expect(mutation_response['mergeRequest']['milestone']).to be_nil
     end
   end
+
+  context 'when passing an invalid milestone_id' do
+    let(:input) { { milestone_id: GitlabSchema.id_from_object(create(:milestone)).to_s } }
+
+    it 'does not set the milestone' do
+      post_graphql_mutation(mutation, current_user: current_user)
+
+      expect(response).to have_gitlab_http_status(:success)
+      expect(graphql_errors).to include(
+        a_hash_including(
+          'message' => "The resource that you are attempting to access does not exist " \
+                       "or you don't have permission to perform this action"
+        )
+      )
+    end
+  end
 end