Practical experience with test-driven development during commissioning of the multi-star AO system ARGOS

Abstract

Commissioning time for an instrument at an observatory is precious, especially the night time. Whenever astronomers come up with a software feature request or point out a software defect, the software engineers have the task to find a solution and implement it as fast as possible. In this project phase, the software engineers work under time pressure and stress to deliver a functional instrument control software (ICS). The shortness of development time during commissioning is a constraint for software engineering teams and applies to the ARGOS project as well. The goal of the ARGOS (Advanced Rayleigh guided Ground layer adaptive Optics System) project is the upgrade of the Large Binocular Telescope (LBT) with an adaptive optics (AO) system consisting of six Rayleigh laser guide stars and wavefront sensors. For developing the ICS, we used the technique TestDriven Development (TDD) whose main rule demands that the programmer writes test code before production code. Thereby, TDD can yield a software system, that grows without defects and eases maintenance. Having applied TDD in a calm and relaxed environment like office and laboratory, the ARGOS team has profited from the benefits of TDD. Before the commissioning, we were worried that the time pressure in that tough project phase would force us to drop TDD because we would spend more time writing test code than it would be worth. Despite this concern at the beginning, we could keep TDD most of the time also in this project phase This report describes the practical application and performance of TDD including its benefits, limitations and problems during the ARGOS commissioning. Furthermore, it covers our experience with pair programming and continuous integration at the telescope.Keywords: Test-Driven Development, TDD, commissioning, continuous integration, pair programming, software engineering, testing, instrument control software, distributed software system, adaptive optics, LBT SET UPThe goal of the multi-star AO system ARGOS is improving the image quality for the imager and spectrograph LUCI. In order to run a complex distributed hardware system like ARGOS, the telescope operators require assistance from the instrument control software (ICS) that the software engineers have to develop partly at the telescope on the mountain under the harsh conditions of an instrument commissioning.

Status of the ARGOS project

“…In addition to the control loop software there are of course a huge amount of devices to control, set, supervise and monitor. Details on the software development can be found in [11].The loops are the following:…”