PHPSA\Variable::incSets PHP Method

    public function incSets()
    {
        return $this->sets++;
    }

 public function testIsUnusedTrue()
 {
     $variable = new Variable('a', 1, CompiledExpression::INTEGER);
     static::assertTrue($variable->isUnused());
     $variable = new Variable('a', null, CompiledExpression::UNKNOWN);
     $variable->incSets();
     static::assertTrue($variable->isUnused());
 }