Refactor StackTracesController specs

* Rearrange tests
* Remove duplication by extracting into before block

spec/controllers/projects/error_tracking/stack_traces_controller_spec.rb

@@ -12,8 +12,7 @@ describe Projects::ErrorTracking::StackTracesController do
   end
 
   describe 'GET #index' do
-    let_it_be(:issue_id) { 1234 }
-
+    let(:issue_id) { 1234 }
     let(:issue_stack_trace_service) { spy(:issue_stack_trace_service) }
 
     subject(:get_stack_trace) do
@@ -24,33 +23,28 @@ describe Projects::ErrorTracking::StackTracesController do
       expect(ErrorTracking::IssueLatestEventService)
         .to receive(:new).with(project, user, issue_id: issue_id.to_s)
         .and_return(issue_stack_trace_service)
+      expect(issue_stack_trace_service).to receive(:execute).and_return(service_response)
+
+      get_stack_trace
     end
 
     context 'awaiting data' do
-      before do
-        expect(issue_stack_trace_service).to receive(:execute)
-          .and_return(status: :error, http_status: :no_content)
-      end
-
-      it 'returns no data' do
-        get_stack_trace
+      let(:service_response) { { status: :error, http_status: :no_content }}
 
+      it 'responds with no data' do
         expect(response).to have_gitlab_http_status(:no_content)
       end
     end
 
     context 'service result is successful' do
-      before do
-        expect(issue_stack_trace_service).to receive(:execute)
-          .and_return(status: :success, latest_event: error_event)
-
-        get_stack_trace
-      end
-
+      let(:service_response) { { status: :success, latest_event: error_event } }
       let(:error_event) { build(:error_tracking_error_event) }
 
-      it 'returns an error' do
+      it 'responds with success' do
         expect(response).to have_gitlab_http_status(:ok)
+      end
+
+      it 'responds with error' do
         expect(response).to match_response_schema('error_tracking/issue_stack_trace')
       end
 
@@ -65,34 +59,26 @@ describe Projects::ErrorTracking::StackTracesController do
       let(:error_message) { 'error message' }
 
       context 'without http_status' do
-        before do
-          expect(issue_stack_trace_service).to receive(:execute)
-            .and_return(status: :error, message: error_message)
-        end
-
-        it 'returns 400 with message' do
-          get_stack_trace
+        let(:service_response) { { status: :error, message: error_message } }
 
+        it 'responds with bad request' do
           expect(response).to have_gitlab_http_status(:bad_request)
+        end
+
+        it 'responds with error message' do
           expect(json_response['message']).to eq(error_message)
         end
       end
 
       context 'with explicit http_status' do
         let(:http_status) { :no_content }
+        let(:service_response) { { status: :error, message: error_message, http_status: http_status } }
 
-        before do
-          expect(issue_stack_trace_service).to receive(:execute).and_return(
-            status: :error,
-            message: error_message,
-            http_status: http_status
-          )
+        it 'responds with custom http status' do
+          expect(response).to have_gitlab_http_status(http_status)
         end
 
-        it 'returns http_status with message' do
-          get_stack_trace
-
-          expect(response).to have_gitlab_http_status(http_status)
+        it 'responds with error message' do
           expect(json_response['message']).to eq(error_message)
         end
       end