+#[cfg(test)]
+#[derive(Default)]
+struct Hand {
+ cards: Vec<Card>,
+}
+#[cfg(test)]
+impl Hand {
+ fn add(&mut self, card: Card) {
+ self.cards.push(card);
+ }
+ fn remove(&mut self, card: Card) -> Result<(), &'static str> {
+ let i = self
+ .cards
+ .iter()
+ .position(|&e| e == card)
+ .ok_or("That card is not in your hand")?;
+ self.cards.swap_remove(i);
+ Ok(())
+ }
+}
+