我正在扑朔迷离地学习TDD（测试驱动开发）。在这里，我试图解析我的JSON数据，但是每次运行测试时，我都会得到一个错误提示。

  

错误：类型'String'不是'索引'的类型'int'的子类型

这些是我的代码

  

weather_app_model_test.dart

  group('fromJson',() {
    test('should return a valid model',() async {
      final Map<String,dynamic> jsonmap =
          json.decode(fixture('weather_app.json'));
      final result = WeatherAppModel.fromJson(jsonmap);
      expect(result,tWeatherAppModel);
    });
  });

  

weather_app_model.dart

factory WeatherAppModel.fromJson(Map<String,dynamic> json) {
    return WeatherAppModel(
      weatherMain: json['weather']['main'],weatherDescription: json['weather']['description'],temp: json['main']['temp'],minTemp: json['main']['temp_min'],maxTemp: json['main']['temp_main'],country: json['sys']['country'],);
  }

  

fixtures / weather_app.json

{
  "coord": {
    "lon": 78,"lat": 20
  },"weather": [
    {
      "id": 500,"main": "Rain","description": "light rain","icon": "10d"
    }
  ],"base": "model","main": {
    "temp": 301.51,"pressure": 1014,"humidity": 67,"temp_min": 301.51,"temp_max": 301.51,"sea_level": 1014,"grnd_level": 979
  },"wind": {
    "speed": 3.19,"deg": 77
  },"rain": {
    "3h": 1.81
  },"clouds": {
    "all": 45
  },"dt": 1572672029,"sys": {
    "country": "IN","sunrise": 1572655775,"sunset": 1572696807
  },"timezone": 19800,"id": 1272596,"name": "Digras","cod": 200
}

任何帮助都会很棒。