implemented proper error handling, added README

src/arguments.rs

@@ -1,3 +1,4 @@
+use anyhow::{bail, Result};
 use clap::Parser;
 
 #[derive(Parser, Default, Debug)]
@@ -22,11 +23,40 @@ pub struct Arguments {
 }
 
 impl Arguments {
-    pub fn validate(&self) -> Result<(), Box<dyn std::error::Error>> {
+    pub fn validate(&self) -> Result<()> {
         if self.action == "up" || self.action == "down" {
             return Ok(());
         }
 
-        Err("Action values are up or down.".into())
+        bail!("Action values are up or down.")
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn args_with_action(action: &str) -> Arguments {
+        Arguments {
+            project: "test".to_string(),
+            action: action.to_string(),
+            legacy: false,
+        }
+    }
+
+    #[test]
+    fn validate_accepts_up() {
+        assert!(args_with_action("up").validate().is_ok());
+    }
+
+    #[test]
+    fn validate_accepts_down() {
+        assert!(args_with_action("down").validate().is_ok());
+    }
+
+    #[test]
+    fn validate_rejects_invalid() {
+        let err = args_with_action("start").validate().unwrap_err();
+        assert!(err.to_string().contains("up or down"));
     }
 }