public function testconcatenate()
{
$my_string = "Hello";
$right_string = " World";
$string = new williamknauss\String($my_string);
$string->concatenate($right_string);
//assert 1
$this->assertEquals($my_string . $right_string, $string->__toString());
$my_string = "World";
$left_string = "Hello ";
$string = new williamknauss\String($my_string);
$string->concatenate($left_string, "LEFT");
//assert 2
$this->assertEquals($left_string . $my_string, $string->__toString());
$my_string = "William";
$right_string = "Knauss";
$string = new williamknauss\String($my_string);
$string->concatenate($right_string, "RIGHT");
//assert 3
$this->assertEquals($my_string . $right_string, $string->__toString());
$my_string = "Teddy";
$default_string = " Bear";
$string = new williamknauss\String($my_string);
$string->concatenate($default_string, "PURPLE");
//assert 4
$this->assertEquals($my_string . $default_string, $string->__toString());
}