Mutagenesis\Mutation\OperatorAddition::getMutation PHP Метод

    public function getMutation(array $tokens, $index)
    {
        $tokens[$index] = '-';
        return $tokens;
    }

 public function testReturnsTokenEquivalentToSubtractionOperator()
 {
     $mutation = new OperatorAddition(10);
     $this->assertEquals(array(10 => '-'), $mutation->getMutation(array(), 10));
 }