Check out our newest collaborative paper with the Stern and Crocker labs, where a CRM was randomly mutagenized to death and the results analyzed in vivo using a high-throughput robotics platform.
Fuqua, T., Jordan, J., van Breugel, M.E. et al. Dense and pleiotropic regulatory information in a developmental enhancer. Nature (2020). https://doi.org/10.1038/s41586-020-2816-5
This thread, written by the first author, explains it super well.