[nostrademons]

Many of them already do weight contributions to open-source projects heavily, particularly their own open-source projects. I remember that when I was in college, over a decade ago, one of the major reasons to contribute to open-source was to build your resume and develop real connections at companies.

The reason they give you code tests is because very often the type of work you will be doing on the company's proprietary code base is different from fixing bugs & implementing features on an open-source codebase, and they want to ensure that you have the skills to do real coding where there isn't an existing codebase to build off. For example, my referrer at Google was someone who I'd worked on a volunteer PHP-based Harry Potter fandom website with. That's great, but very different from the sort of heavy algorithmic code that much of my work at Google entailed.