public function testIsString()
 {
     // from js
     $this->assertTrue(__u::isString(join(', ', array(1, 2, 3))), 'strings are');
     // extra
     $this->assertFalse(__u::isString(1));
     $this->assertTrue(__u::isString(''));
     $this->assertTrue(__u::isString('1'));
     $this->assertFalse(__u::isString(array()));
     $this->assertFalse(__u::isString(null));
     $this->assertFalse(__u(1)->isString());
     $this->assertTrue(__u('1')->isString());
     $this->assertTrue(__u('')->isString());
     // docs
     $this->assertTrue(__u::isString('moe'));
     $this->assertTrue(__u::isString(''));
 }