ln: add some tests

Author: xtqqczze

Cargo.lock

@@ -386,6 +386,7 @@ version = "0.8.0"
 
 [workspace.dependencies]
 ansi-width = "0.1.0"
+assert_matches = "1.5.0"
 bigdecimal = "0.4"
 binary-heap-plus = "0.5.0"
 bstr = "1.9.1"

Cargo.toml

@@ -25,6 +25,9 @@ uucore = { workspace = true, features = ["backup-control", "fs"] }
 thiserror = { workspace = true }
 fluent = { workspace = true }
 
+[dev-dependencies]
+assert_matches = { workspace = true }
+
 [[bin]]
 name = "ln"
 path = "src/main.rs"

src/uu/ln/Cargo.toml

@@ -536,3 +536,67 @@ fn symlink<P1: AsRef<Path>, P2: AsRef<Path>>(_src: P1, _dst: P2) -> io::Result<(
         "symlinks not supported on this platform",
     ))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use assert_matches::assert_matches;
+    use std::ffi::OsString;
+
+    #[test]
+    fn test_exec_missing_operand() {
+        let settings: Settings = Settings {
+            overwrite: OverwriteMode::NoClobber,
+            backup: BackupMode::None,
+            suffix: OsString::from(""),
+            symbolic: false,
+            relative: false,
+            logical: false,
+            target_dir: None,
+            no_target_dir: false,
+            no_dereference: false,
+            verbose: false,
+        };
+
+        let result = exec(&[], &settings);
+        assert_matches!(result, Err(LnError::MissingOperand));
+    }
+
+    #[test]
+    fn test_exec_missing_destination() {
+        let settings = Settings {
+            overwrite: OverwriteMode::NoClobber,
+            backup: BackupMode::None,
+            suffix: OsString::from(""),
+            symbolic: false,
+            relative: false,
+            logical: false,
+            target_dir: None,
+            no_target_dir: true,
+            no_dereference: false,
+            verbose: false,
+        };
+
+        let result = exec(&["a".into()], &settings);
+        assert_matches!(result, Err(LnError::MissingDestination(path)) if *path == *"a");
+    }
+
+    #[test]
+    fn test_exec_extra_operand() {
+        let settings = Settings {
+            overwrite: OverwriteMode::NoClobber,
+            backup: BackupMode::None,
+            suffix: OsString::from(""),
+            symbolic: false,
+            relative: false,
+            logical: false,
+            target_dir: None,
+            no_target_dir: true,
+            no_dereference: false,
+            verbose: false,
+        };
+
+        let result = exec(&["a".into(), "b".into(), "c".into()], &settings);
+        assert_matches!(result, Err(LnError::ExtraOperand(operand, _)) if operand == "c");
+    }
+}