// line comment
/*
 * block comment
 */
{
  "trailing commas": {
    "lists": {
      "multiple lines": [
        "",
      ]
    },
    "objects": {
      "multiple lines": {
        "key": "",
      }
    }
  },
  "environment variable substitution": {
    "set": {
      "true": "${SET_VAR_TRUE}",
      "false": "${SET_VAR_FALSE}",
      "null": "${SET_VAR_NULL}",
      "undefined": "${SET_VAR_UNDEFINED}",
      "number": "${SET_VAR_NUMBER}",
      "string": "${SET_VAR_STRING}",
      "empty string": "${SET_VAR_EMPTY_STRING}"
    },
    "unset": {
      "no default": "${UNSET_VAR}",
      "true": "${UNSET_VAR:true}",
      "false": "${UNSET_VAR:false}",
      "null": "${UNSET_VAR:null}",
      "undefined": "${UNSET_VAR:undefined}",
      "number": "${UNSET_VAR:123}",
      "string": "${UNSET_VAR:foo}",
      "empty string": "${UNSET_VAR:}"
    }
  }
}