use assert_cmd::prelude::*; use predicates::prelude::*; use std::process::Command; #[test] fn file_doesnt_exist() -> Result<(), Box> { let mut cmd = Command::cargo_bin("package-manager")?; cmd.arg("foobar").arg("test/file/doesnt/exist"); cmd.assert() .failure() .stderr(predicate::str::contains("could not read file")); Ok(()) }