public function testjoin()
{
$my_array = array("Hello", "World");
$string = new williamknauss\String($my_array);
$string->join(" ");
//assert 1
$this->assertEquals(join(" ", $my_array), $string->return_string());
$string = new williamknauss\String("Hello World");
$string->join(" ", $my_array);
//assert 2
$this->assertEquals(join(" ", $my_array), $string->return_string());
}