use assert_cmd::prelude::*; use assert_fs::prelude::*; use predicates::prelude::*; use std::process::Command; #[test] fn file_does_not_exist() -> Result<(), Box> { let mut cmd = Command::cargo_bin("hello-rust")?; cmd.arg("foobar").arg("test/file/doesent/exist"); cmd.assert() .failure() .stderr(predicate::str::contains("Could not read file")); Ok(()) } #[test] fn find_content_in_file() -> Result<(), Box> { let file = assert_fs::NamedTempFile::new("sample.txt")?; file.write_str("A test\nActual content\nMore content\nAnother test")?; let mut cmd = Command::cargo_bin("hello-rust")?; cmd.arg("test").arg(file.path()); cmd.assert() .success() .stdout(predicate::str::contains("A test\nAnother test")); Ok(()) }