Add test case for old AVL Tree crash

Author: hollance

AVL Tree/AVLTree.playground/Sources/AVLTree.swift

@@ -207,7 +207,7 @@ extension AVLTree {
     let lrFactor = lrDifference(node)
     if lrFactor > 1 {
       // left-left or left-right
-      if (lrDifference(node.leftChild) > 0) {
+      if lrDifference(node.leftChild) > 0 {
         // left-left
         nodes[0] = node
         nodes[2] = node.leftChild
@@ -270,7 +270,6 @@ extension AVLTree {
       nodes[2]?.parent = nodeParent
     }
 
-
     nodes[2]?.leftChild = nodes[1]
     nodes[1]?.parent = nodes[2]
     nodes[2]?.rightChild = nodes[0]
@@ -289,7 +288,6 @@ extension AVLTree {
     updateHeightUpwards(nodes[1])    // Update height from left
     updateHeightUpwards(nodes[0])    // Update height from right
 
-
     balance(nodes[2]?.parent)
   }
 }
@@ -415,4 +413,4 @@ extension AVLTree: CustomStringConvertible {
       return "[]"
     }
   }
-}
+}

AVL Tree/AVLTree.swift

@@ -207,7 +207,7 @@ extension AVLTree {
     let lrFactor = lrDifference(node)
     if lrFactor > 1 {
       // left-left or left-right
-      if (lrDifference(node.leftChild) > 0) {
+      if lrDifference(node.leftChild) > 0 {
         // left-left
         nodes[0] = node
         nodes[2] = node.leftChild
@@ -270,7 +270,6 @@ extension AVLTree {
       nodes[2]?.parent = nodeParent
     }
 
-
     nodes[2]?.leftChild = nodes[1]
     nodes[1]?.parent = nodes[2]
     nodes[2]?.rightChild = nodes[0]
@@ -289,7 +288,6 @@ extension AVLTree {
     updateHeightUpwards(nodes[1])    // Update height from left
     updateHeightUpwards(nodes[0])    // Update height from right
 
-
     balance(nodes[2]?.parent)
   }
 }
@@ -415,4 +413,4 @@ extension AVLTree: CustomStringConvertible {
       return "[]"
     }
   }
-}
+}

AVL Tree/Tests/AVLTreeTests.swift

@@ -68,38 +68,61 @@ class AVLTreeTests: XCTestCase {
       self.tree?.search(400)
     }
   }
+  
+  func testMinimumOnPopulatedTree() {
+    self.tree?.autopopulateWithNodes(500)
+    let min = self.tree?.root?.minimum()
+    XCTAssertNotNil(min, "Minimum function not working")
+  }
+  
+  func testMinimumOnSingleTreeNode() {
+    let treeNode = TreeNode(key: 1, payload: "A")
+    let min = treeNode.minimum()
 
-    func testMinimumOnPopulatedTree() {
-        self.tree?.autopopulateWithNodes(500)
-        let min = self.tree?.root?.minimum()
-        XCTAssertNotNil(min, "Minimum function not working")
-    }
-    
-    func testMinimumOnSingleTreeNode() {
-        let treeNode = TreeNode(key: 1, payload: "A")
-        let min = treeNode.minimum()
-        
-        XCTAssertNotNil(min, "Minimum on single node should be returned")
-        XCTAssertEqual(min?.payload,treeNode.payload)
-    }
+    XCTAssertNotNil(min, "Minimum on single node should be returned")
+    XCTAssertEqual(min?.payload,treeNode.payload)
+  }
+  
+  func testDeleteExistentKey() {
+    self.tree?.delete(1)
+    XCTAssertNil(self.tree?.search(1), "Key should not exist anymore")
+  }
+  
+  func testDeleteNotExistentKey() {
+    self.tree?.delete(1056)
+    XCTAssertNil(self.tree?.search(1056), "Key should not exist")
+  }
+  
+  func testDelete() {
+    let permutations = [
+      [5, 1, 4, 2, 3],
+      [2, 3, 1, 5, 4],
+      [4, 5, 3, 2, 1],
+      [3, 2, 5, 4, 1],
+    ]
 
-    func testDeleteExistentKey() {
-        self.tree?.delete(1)
-        XCTAssertNil(self.tree?.search(1), "Key should not exist anymore")
-    }
+    for p in permutations {
+      let tree = AVLTree<Int, String>()
 
-    func testDeleteNOTExistentKey() {
-        self.tree?.delete(1056)
-        XCTAssertNil(self.tree?.search(1056), "Key should not exist")
+      tree.insert(1, "five")
+      tree.insert(2, "four")
+      tree.insert(3, "three")
+      tree.insert(4, "two")
+      tree.insert(5, "one")
+      
+      for i in p {
+        tree.delete(i)
+      }
     }
-
+  }
 }
 
 extension AVLTree where Key : SignedIntegerType {
   func autopopulateWithNodes(count : Int) {
     var k : Key = 1
     for _ in 0...count {
-      self.insert(k++)
+      self.insert(k)
+      k = k + 1
     }
   }
 }