1 files changed, 111 insertions, 0 deletions
diff --git a/spec/requests/api/graphql/merge_request/merge_request_spec.rb b/spec/requests/api/graphql/merge_request/merge_request_spec.rb
new file mode 100644
index 00000000000..75dd01a0763
--- /dev/null
+++ b/spec/requests/api/graphql/merge_request/merge_request_spec.rb
@@ -0,0 +1,111 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'Query.merge_request(id)' do
+  include GraphqlHelpers
+
+  let_it_be(:project) { create(:project, :empty_repo) }
+  let_it_be(:merge_request) { create(:merge_request, source_project: project) }
+  let_it_be(:current_user) { create(:user) }
+  let_it_be(:merge_request_params) { { 'id' => merge_request.to_global_id.to_s } }
+
+  let(:merge_request_data) { graphql_data['mergeRequest'] }
+  let(:merge_request_fields) { all_graphql_fields_for('MergeRequest'.classify) }
+
+  let(:query) do
+    graphql_query_for('mergeRequest', merge_request_params, merge_request_fields)
+  end
+
+  it_behaves_like 'a working graphql query' do
+    before do
+      post_graphql(query, current_user: current_user)
+    end
+  end
+
+  it_behaves_like 'a noteable graphql type we can query' do
+    let(:noteable) { merge_request }
+    let(:project) { merge_request.project }
+    let(:path_to_noteable) { [:merge_request] }
+
+    before do
+      project.add_reporter(current_user)
+    end
+
+    def query(fields)
+      graphql_query_for('mergeRequest', merge_request_params, fields)
+    end
+  end
+
+  context 'when the user does not have access to the merge request' do
+    it 'returns nil' do
+      post_graphql(query)
+
+      expect(merge_request_data).to be nil
+    end
+  end
+
+  context 'when the user does have access' do
+    before do
+      project.add_reporter(current_user)
+    end
+
+    it 'returns the merge request' do
+      post_graphql(query, current_user: current_user)
+
+      expect(merge_request_data).to include(
+        'title' => merge_request.title,
+        'description' => merge_request.description
+      )
+    end
+
+    context 'when selecting any single field' do
+      where(:field) do
+        scalar_fields_of('MergeRequest').map { |name| [name] }
+      end
+
+      with_them do
+        it_behaves_like 'a working graphql query' do
+          let(:merge_request_fields) do
+            field
+          end
+
+          before do
+            post_graphql(query, current_user: current_user)
+          end
+
+          it "returns the merge request and field #{params['field']}" do
+            expect(merge_request_data.keys).to eq([field])
+          end
+        end
+      end
+    end
+
+    context 'when selecting multiple fields' do
+      let(:merge_request_fields) { ['title', 'description', 'author { username }'] }
+
+      it 'returns the merge request with the specified fields' do
+        post_graphql(query, current_user: current_user)
+
+        expect(merge_request_data.keys).to eq %w[title description author]
+        expect(merge_request_data['title']).to eq(merge_request.title)
+        expect(merge_request_data['description']).to eq(merge_request.description)
+        expect(merge_request_data['author']['username']).to eq(merge_request.author.username)
+      end
+    end
+
+    context 'when passed a non-merge request gid' do
+      let(:issue) { create(:issue) }
+
+      it 'returns an error' do
+        gid = issue.to_global_id.to_s
+        merge_request_params['id'] = gid
+
+        post_graphql(query, current_user: current_user)
+
+        expect(graphql_errors).not_to be nil
+        expect(graphql_errors.first['message']).to eq("\"#{gid}\" does not represent an instance of MergeRequest")
+      end
+    end
+  end
+end