Add tests and fix find bug.

src/bst.rs

@@ -33,8 +33,8 @@ impl<T: Ord> BinarySearchTree<T> {
         }
     }
 
-    pub fn find(&mut self, data: T) -> Option<T> {
-        self.root.take().map(|mut root| root.find(data))?
+    pub fn find(&self, data: T) -> Option<T> {
+        self.root.as_ref().map(|root| root.find(data))?
     }
 }
 
@@ -66,11 +66,43 @@ impl<T: Ord> Node<T> {
         }
     }
 
-    fn find(&mut self, data: T) -> Option<T> {
+    fn find(&self, data: T) -> Option<T> {
         match self.data.cmp(&data) {
-            Less => self.right.take().map(|mut right| right.find(data))?,
+            Less => self.right.as_ref().map(|right| right.find(data))?,
             Equal => Some(data),
-            Greater => self.left.take().map(|mut left| left.find(data))?,
+            Greater => self.left.as_ref().map(|left| left.find(data))?,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn insert_and_find() {
+        let mut tree = BinarySearchTree::new();
+        tree.insert(1);
+        assert_eq!(tree.find(1), Some(1));
+    }
+
+    #[test]
+    fn insert_three_values_find_third() {
+        let mut tree = BinarySearchTree::new();
+        for num in [1, 2, 3] {
+            tree.insert(num);
+        }
+        assert_eq!(tree.find(3), Some(3));
+    }
+
+    #[test]
+    fn multiple_finds() {
+        let mut tree = BinarySearchTree::new();
+        for num in [1, 2, 3] {
+            tree.insert(num);
+        }
+        for num in [1, 2, 3] {
+            assert_eq!(tree.find(num), Some(num));
         }
     }
 }