The latest post from Kai Nacke shows how to use a fuzz-testing tool called American Fuzzy Lop in conjunction with LDC to fuzz test your D programs.

The blog:
https://dlang.org/blog/2019/06/25/fuzzing-your-d-application-with-ldc-and-afl/

Reddit:
https://www.reddit.com/r/programming/comments/c5amie/fuzzing_your_d_application_with_ldc_and_american/