Delphi XE JSON Update

I recently updated my JSON-Library. Both, IJSONObject and IJSONArray now have methods to check for the type of the nested items.

IJSONObject = interface
['{D00A665F-3CBB-4DDB-8300-FB8020DA564B}']
  .
  .
  .
  function isJSONObject(aKey : string) : boolean;
  function isJSONArray(aKey : string) : boolean;
  function isString(aKey : string) : boolean;
  function isInteger(aKey : string) : boolean;
  function isBoolean(aKey : string) : boolean;
  function isDouble(aKey : string) : boolean;
end;

IJSONArray = interface
['{B120D59A-1D00-469E-97CE-AE2A635A51ED}']
  .
  .
  .
  function isJSONObject(aIndex : integer) : boolean;
  function isJSONArray(aIndex : integer) : boolean;
  function isString(aIndex : integer) : boolean;
  function isInteger(aIndex : integer) : boolean;
  function isBoolean(aIndex : integer) : boolean;
  function isDouble(aIndex : integer) : boolean;
end;

Usage:

var
  jo : IJSONObject;
begin
  jo := TJSON.NewObject('{"string":"abc", "integer":123}');

  jo.isString('string'); // true
  jo.isInteger('integer'); // true
  jo.isBoolean('string'); // false
end;

The implementation is very strict, e.g. isDouble will return false if the value is an integer and could be accessed as a double. I also included unit tests to cover these methods.