{"id":2021,"date":"2016-02-04T19:41:48","date_gmt":"2016-02-04T18:41:48","guid":{"rendered":"https:\/\/www.opengis.ch\/?p=2021"},"modified":"2020-04-29T18:57:33","modified_gmt":"2020-04-29T16:57:33","slug":"increasing-the-stability-of-processing-algorithms","status":"publish","type":"post","link":"https:\/\/www.opengis.ch\/fr\/2016\/02\/04\/increasing-the-stability-of-processing-algorithms\/","title":{"rendered":"Increasing the stability of processing algorithms"},"content":{"rendered":"

Processing just got a new testing framework to improve\u00a0the long-term stability of this important plugin. And you can help to improve it, even if you are not a software developer!<\/strong>
\nThis is yet another piece in our never-stopping crusade to improve the stability and quality of the best\u00a0desktop GIS on the market.<\/p>\n

Processing<\/h2>\n

You probably know processing<\/a>. If you don’t: processing is the number one plugin to enable after every QGIS installation. It offers a very wide variety of geo-algorithms from generic one to very task-specific tools and allows building models and to completely automate workflows this way.
\nProcessing is being improved consistently and gets better with every release. But like always in software development, there is a risk, that an improvement can have undesired side-effects which break previously working parts of an application.<\/p>\n

Unit Testing and Continuous Integration<\/h2>\n

A bit more over a year ago (when working still as a freelancer) I started a crowdfunding initiative for automated testing<\/a>, a technique in software engineering also known as continuous integration. With every single change a developer does to an application, a number of functions – so called unit tests – are run and their outcome is compared to a known-good control dataset. This way side-effects can be detected early on and fixed before they get deployed to productive environments.
\nThis has been an amazing story of success. Since it has been put into place a lot of new unit tests have been added to a lot of QGIS functionality. A lot of bugs\u00a0have been discovered by some servers that consistently test all the cool new stuff that comes in. Meanwhile we arrived at a point where we even test meta-quality of our codebase that makes the life for plugin developers easier: are new functions available from python? And do they come with documentation?
\n\"pr\"<\/a>
\nHowever, until now processing was excluded from these checks. But no longer.
\nTo demonstrate the importance of this, take the intersection algorithm. Some months ago it started to fail in certain scenarios, caused by an update on the geometry engine. A totally unrelated change suddenly made the intersection algorithm behave differently. It just produced faulty results. The only thing was a small warning in the message log, a well-hidden place where you normally don’t check for warnings.
\nA small numbers of tests are already in place and make sure that the following algorithms run properly:<\/p>\n