test: Add unknown arg init test

Author: epage

tests/suite/cli_rustup_init_ui.rs

@@ -27,6 +27,27 @@ fn test_help(name: &str, args: &[&str]) {
         .stderr_eq("");
 }
 
+#[track_caller]
+fn test_error(name: &str, args: &[&str]) {
+    let home = Path::new(env!("CARGO_TARGET_TMPDIR")).join("home-ro");
+    create_dir_all(&home).unwrap();
+
+    let rustup_init = snapbox::cmd::cargo_bin!("rustup-init");
+    Command::new(rustup_init)
+        .env("RUSTUP_TERM_COLOR", "always")
+        // once installed rustup asserts the presence of ~/.rustup/settings.toml if
+        // Config is instantiated.
+        .env("HOME", &home)
+        .args(args)
+        .assert()
+        .failure()
+        .stdout_eq("")
+        .stderr_eq(Data::read_from(
+            Path::new(&format!("tests/suite/cli_rustup_ui/{name}.stderr.term.svg")),
+            None,
+        ));
+}
+
 #[track_caller]
 #[cfg(not(target_os = "windows"))] // On windows, we don't use rustup-init.sh
 fn test_sh_help(name: &str, args: &[&str]) {
@@ -57,6 +78,11 @@ fn rustup_init_help_flag() {
     test_help("rustup_init_help_flag", &["--help"]);
 }
 
+#[test]
+fn rustup_init_unknown_arg() {
+    test_error("rustup_init_unknown_arg", &["--random"]);
+}
+
 #[test]
 #[cfg(not(target_os = "windows"))] // On windows, we don't use rustup-init.sh
 fn rustup_init_sh_help_flag() {