It's used only as a dev dependency in 6 crates.

Depender (with downloads and own rev deps) RegexTest version
21.9M 61 regex-automata dev ^0.1.0
16.8M 10292 regex dev ^0.1.0
2.4M 442 regex-lite dev ^0.1.0
4.0K 1 regex-cursor dev ^0.1.0
130 2 kbnf-regex-automata dev ^0.1.0
supply-chain-trust-example-crate-000021 dev ^0.1.0