{
let test = new RedBlackTree();
if (test.contains('key1')) throw 'Function contains is not working.';
test.put('key1', 'val1');
if (!test.contains('key1')) throw 'Function contains is not working.';
test.put('key3', 'val3');
test.put('key2', 'val2');
test.put('key2', 'val4');
return test.keys().map(key => test.get(key));
}