Cargo Features

Gds21 has no features set by default.

[dependencies]
gds21 = { version = "3.0.0-pre.2", features = ["selftest"] }
selftest = tempfile

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

tempfile selftest?