anchor.diff:        "device-id": "{optional}",
         "model-name": "{optional}",
         "os-version": "{optional}",
  -      "api-level": "{optional}",
         "screen-size": "{optional}",
         "app-root": "{required}",
         "app-path": "{required}"
  
positive.code: 
  const String specGuide =
  'Everything in the curly braces can be replaced with your own value.\n'
  '"device-id", "model-name", "os-version", "api-level" and "screem-size" '
  'are optional.\n'
  '"app-root" and "app-path" are required.\n'
  'An example spec would be\n'
  '''
  
negative.code:       "device-id": "HT4CWJT03204",
        "model-name": "Nexus 9",
        "os-version": "6.0",
        "screen-size": "xlarge",
        "app-root": "/path/to/flutter-app",
        "app-path": "/path/to/main.dart"
  