function testRegexJokeExpression() {
// how many regex does it take to change a lightbulb
// correct answer, any non-zero digit
$regex = '/\d(?<!0)/';
$this->assertFalse(preg_match($regex,'0'));
$this->assertTrue(preg_match($regex,'1'));
$this->assertTrue(preg_match($regex,'10'));
//another suggested regex
$regex = '/\d(?!0)/';
// this test fails with your regex
$this->assertFalse(preg_match($regex,'0'), 'fails to fail for case 0');
$this->assertTrue(preg_match($regex,'1'));
$this->assertTrue(preg_match($regex,'10'));
//modified this way, it actually would work
$regex = '/(?!0)\d/';
$this->assertFalse(preg_match($regex,'0'));
$this->assertTrue(preg_match($regex,'1'));
$this->assertTrue(preg_match($regex,'10'));
}