As open source and agile development do work in some circumstances, particularly with regard to shorter and more frequent release policy, we wonder whether the defect profile (reliability growth) found in the open-source projects so far is typical of open-source software development or of software developed iteratively and incrementally. To investigate this, we examined an open source web testing tool developed by an agile leading company. The results of this analysis indicate two findings. First, it supports the tentative findings that iteratively developed software does not exhibit a standard reliability growth in the defect modeling, and second, somewhat surprisingly that the defect density is reducing, as a sign of improving in quality yet the normal measure of software reliability are not useful
