使用嵌入的子文档保存mongoose父模型

Question

这些是我的架构

    // in test schema file
    const Test = new mongoose.Schema(
      {
        _id: { type: String, default: uuid.v1 },
        responses: [Response]
      },
      {
        timestamps: true
      }
    );


    // in response schema file 
    const Response = new mongoose.Schema({
      _id: { type: String, default: uuid.v1 },
      answer: {
        type: String,
        enum: [
          "StronglyAgree",
          "Agree",
          "SomewhatAgree",
          "Neutral",
          "SomewhatDisagree",
          "Disagree",
          "StronglyDisagree"
        ]
      },
      question: { type: String, ref: "Question" }
    });

我尝试输入对我的测试的反应，如此

  async create() {
    try {
      const test = new this.model({ _id: uuid.v1() });
      const questions = await this.questionModel.getAllQuestions();

      questions.forEach(question => {
        test.responses.push({
          question: question._id,
          answer: "StronglyAgree"
        });
      });
      var savedTest = await test.save();
      savedTest = await this.model.populate(test, {
        path: "responses.question"
      });

      return savedTest;
    } catch (e) {
      throw e;
    }
  }

我收到此错误

 { responses: 
      MongooseError {
        message: 'Cast to Array failed for value "1" at path "responses"',
        name: 'CastError',
        stringValue: '"1"',
        kind: 'Array',
        value: 1,
        path: 'responses',
        reason: [Object] } },
  _message: 'Test validation failed',
  name: 'ValidationError' }

为什么会这样？