PHPUnit test have to check every case

Code
<?php

use PHPUnit\Framework\TestCase;

/**
 * The exception test case with
 * second parameter 0 isn't even enough.
 */
class DivideTest extends TestCase
{
    public function 
testCalcException() : void
    
{
        
$this->expectException('\InvalidArgumentException');
        
$divide = new Divide();
        
$divide->calc(10);
    }
}

class 
Divide
{
    public function 
calc($dividend$divisor)
    {
        if (
== $divisor) {
            throw new 
InvalidArgumentException('you really want to divide
                with 0? Are you serious?'
);
        }
        
        return 
$dividend $divisor;
    }
}
Result
Time: 217 ms, Memory: 16.00 MB

OK (1 test, 0 assertions)