removed test typo and added docstrings for new utility functions

Author: souma4

src/binarytree.jl

@@ -148,6 +148,16 @@ end
 #  UTILITIES
 # -----------
 
+"""
+  BinaryTrees.minnode(tree)
+
+Find the `node` with the smallest `key` in the `tree`.
+
+  BinaryTrees.minnode(node)
+
+Find the `node` with the smallest `key` in the subtree rooted at `node`.
+If `nothing` is provided, `nothing` is returned.
+"""
 minnode(tree::BinaryTree) = minnode(root(tree))
 
 function minnode(node::BinaryNode)
@@ -157,6 +167,16 @@ end
 
 minnode(node::Nothing) = nothing
 
+"""
+  BinaryTrees.maxnode(tree)
+
+Find the `node` with the maximum `key` in the `tree`.
+
+  BinaryTrees.maxnode(node)
+
+Find the `node` with the maximum `key` in the subtree rooted at `node`.
+If `nothing` is provided, `nothing` is returned.
+"""
 maxnode(tree::BinaryTree) = maxnode(root(tree))
 
 function maxnode(node::BinaryNode)
@@ -166,6 +186,15 @@ end
 
 maxnode(node::Nothing) = nothing
 
+"""
+  BinaryTrees.prevnext(tree, k)
+
+Returns a `tuple` of each `node` immediately before
+and after the `node` with `key`, `k` within `tree`.
+
+If an adjacent `node` does not exist, `nothing` is returned in its place.
+If `k` is `nothing`, returns `(nothing, nothing)`.
+"""
 function prevnext(tree::BinaryTree, k)
   prev, next = nothing, nothing
   current = root(tree)

test/runtests.jl

@@ -261,7 +261,6 @@ const BT = BinaryTrees
     @inferred Nothing BT.prevnext(tree, 2)[2]
     @inferred BT.prevnext(tree, nothing)
     @inferred Nothing BT.search(tree, 2)
-    @inferred Nothing BT.search(tree, 2)
     @inferred Nothing BT.search(tree, 1)
     @inferred Nothing BT.search(tree, 3)
     @inferred BT.delete!(tree, 2)