ReLucBlog

On March 6, 2020, a Lizmap user identified a regression in QGIS Server 3.10 compared to version 3.4. This regression concerns the print function (GetPrint) for the layer groups configured as a single layer for Lizmap. A group configured as a layer could no longer be printed with QGIS Server 3.10.

To correct this bug, we decided to use Test Driven Developments. We started by creating a new test for QGIS Server highlighting the regression. We then corrected this regression and verified using the test that the patch we proposed corrected the test.

The problem is that once the patch and the new test were integrated into the master branch (development version) and the release-3_12 branch (version 3.12) of QGIS, the Travis-based continuous integration system used by QGIS indicated regularly have a problem with testing the QGIS Server print function. Regression correction was therefore not included in version 3.10 of QGIS which is the long term released version (LTR), and tests of the printing function of QGIS Sever were blacklisted for the continuous integration. In fact the test indicated a Segfault.

It took QGIS Server developers several months, PR 36198, PR 36581, PR 37179, to identify the reason why testing of the QGIS Server print function was failed in continuous integration. The reason was simple: the test was too long, it exceeded 55 seconds fc561d0
on travis in continuous integration.

It is true that the test file started to be too long. The solution to be able to reactivate the tests in continuous integration was to separate the tests of the printing function of QGIS Server in several tests.

Once the tests of the printing function reactivated for the master branch and the release-3_14 branch, the regression patch could be integrated into the release-3_10 branch (version 3.10 of QGIS) and this patch will be available when the release of version 3.10.8 on July 17, 2020.