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To the extent that students are writing code: a high quality "autograder" test suite. A tight feedback loop on the correctness of your work/understanding is the most powerful learning aid I've ever encountered.

Although it's a step on the right direction, I'm not a fan of Coursera's "upload a zip file and wait 10 minutes" approach: even that much delay means you've lost your mental "working set" by the time feedback comes. My college professors would give those to us as Make targets in the project scaffolds, which made it closer to "TDD."

In a similar vein, thoughtfully designed interactive environments with good difficulty progression, like Micro-corruption [0]. It's easy to imagine something like this for data science (here's an RStudio workbench and a dataset, go find the needle in the haystack, etc).

[0] https://microcorruption.com/login