[astro_robot]

Eh, I feel like this is pretty bland. It should incorporate a dictionary attack database. For example, "password" should be considered way weaker than any combination of letters. I would look at https://howsecureismypassword.net/ for inspiration.

[kbirkeland]

Dropbox's zxcvbn[1] seems to do a good job of this along with detecting sequences and keyboard patterns.

[1] https://github.com/dropbox/zxcvbn