This paper introduces the interactive prototype of an online domain-specific language laboratory (DSL-Lab) to test the usability of different end-user programming languages at scale. It is a web-based ecosystem that simulates different robotic environments and supports various programming languages. The ecosystem provides a controlled experimental environment where only selected variables, like the programming language, are interchanged, eliminating confounding factors such as differences in editor features, console displays, or test setups that might influence user experience and performance metrics. The system features an editor, integrated console, robot simulation, task manager, and automatic metrics collection, and it is built over an extensible architecture where components can be changed and features can be specifically added to the given test setup. DSL-Lab makes an important contribution towards scalable, consistent, and configurable user studies, largely facilitating quantitative data collection across multiple testing sessions.