fix error message, add test

crates/servicepoint/src/connection.rs

@@ -80,3 +80,16 @@ impl Connection {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::packet::*;
+
+    #[test]
+    fn send_fake() {
+        let data: &[u8] = &[0u8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
+        let packet = Packet::try_from(data).unwrap();
+        Connection::Fake.send(packet).unwrap()
+    }
+}

crates/servicepoint/src/grid.rs

@@ -79,12 +79,12 @@ pub trait Grid<T> {
         assert!(
             x < self.width(),
             "cannot access index [{x}, {y}] because x is outside of bounds 0..{}",
-            self.width()
+            self.width() - 1
         );
         assert!(
             y < self.height(),
-            "cannot access byte [{x}, {y}] because y is outside of bounds 0..{}",
-            self.height()
+            "cannot access index [{x}, {y}] because y is outside of bounds 0..{}",
+            self.height() - 1
         );
     }
 }