diff --git a/src/world.rs b/src/world.rs
index 357b82d..43afa6e 100644
--- a/src/world.rs
+++ b/src/world.rs
@@ -3,3 +3,31 @@ pub struct World {
     pub x: i32,
     pub y: i32,
 }
+
+pub fn is_instruction(v: &Vec<char>) -> bool {
+    for c in v {
+        match c {
+            'F' => continue,
+            'R' => continue,
+            'L' => continue,
+            _ => return false,
+        }
+    }
+    true
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn is_instruction_test() {
+        let v = vec!['F', 'R', 'L', 'F'];
+        assert!(is_instruction(&v));
+    }
+    #[test]
+    #[should_panic]
+    fn is_instruction_test_fail() {
+        let v = vec!['F', 'R', 'L', 'Z'];
+        assert!(is_instruction(&v));
+    }
+}