Feature/#58comment delete api

.gitignore

@@ -1 +1,2 @@
 infra/env/backend.env
+.idea

backend/app/controllers/comments_controller.rb

@@ -12,6 +12,16 @@ def create
     end
   end
 
+  def destroy
+    comment = Comment.find_by!(id: params[:id], memo_id: params[:memo_id])
+
+    if comment.destroy
+      head :no_content
+    else
+      render json: { errors: comment.errors.full_messages }, status: :unprocessable_entity
+    end
+  end
+
   private
 
   def comment_params

backend/config/routes.rb

@@ -1,5 +1,5 @@
 Rails.application.routes.draw do
   resources :memos, only: %i[index show create update destroy] do
-    resources :comments, only: %i[create]
+    resources :comments, only: %i[create destroy]
   end
 end

backend/spec/requests/comments_spec.rb

@@ -33,4 +33,66 @@
       end
     end
   end
+
+  describe 'DELETE /memos/:memo_id/comments/:id' do
+    context 'コメントが存在する場合' do
+      let!(:memo) { create(:memo) }
+      let!(:comment) { create(:comment, memo: memo) }
+
+      it 'コメントが削除され、204になる' do
+        aggregate_failures do
+          expect do
+            delete "/memos/#{memo.id}/comments/#{comment.id}", as: :json
+          end.to change(Comment, :count).by(-1)
+          expect(response).to have_http_status(:no_content)
+        end
+      end
+    end
+
+    context 'コメントが存在しない場合' do
+      let!(:memo) { create(:memo) }
+
+      it '404が返ることを確認する' do
+        aggregate_failures do
+          expect do
+            delete "/memos/#{memo.id}/comments/0", as: :json
+          end.not_to change(Comment, :count)
+          expect(response).to have_http_status(:not_found)
+        end
+      end
+    end
+
+    context 'メモが存在しない場合' do
+      let!(:memo) { create(:memo) }
+      let!(:comment) { create(:comment, memo: memo) }
+
+      it '404が返ることを確認する' do
+        aggregate_failures do
+          expect do
+            delete "/memos/0/comments/#{comment.id}", as: :json
+          end.not_to change(Comment, :count)
+          expect(response).to have_http_status(:not_found)
+        end
+      end
+    end
+
+    context 'コメントの削除に失敗した場合' do
+      let!(:memo) { create(:memo) }
+      let!(:comment) { create(:comment, memo: memo) }
+
+      before do
+        allow(Comment).to receive(:find_by).and_return(comment)
+        allow(comment).to receive(:destroy).and_return(false)
+      end
+
+      it '422が返ることを確認する' do
+        aggregate_failures do
+          expect do
+            delete "/memos/#{memo.id}/comments/#{comment.id}", as: :json
+          end.not_to change(Comment, :count)
+          expect(response).to have_http_status(:unprocessable_entity)
+        end
+      end
+    end
+  end
 end