It's used only as a dev dependency in 5 crates.

Depender (with downloads and own rev deps) futures-test-preview version
200 4 tari_p2p dev ^0.3.0-alpha.19
120 5 tari_comms_dht dev ^0.3.0-alpha.19
1 tarpc-lib dev ^0.3.0-alpha.18
sendfile dev ^0.3.0-alpha.18
tarpc-json-transport dev ^0.3.0-alpha.18