Add -descendantNodeAtIndexPath: and tests to CPTreeNode

AppKit/CPTreeNode.j

@@ -87,6 +87,18 @@
         [_childNodes[count] sortWithSortDescriptors:sortDescriptors recursively:YES];
 }
 
+- (CPTreeNode)descendantNodeAtIndexPath:(CPIndexPath)indexPath
+{
+    var count = [indexPath length],
+        node = self;
+    
+    for(var i = 0; i < count; i++) {
+        node = [node objectInChildNodesAtIndex:[indexPath indexAtPosition:i]];
+    }
+    
+    return node;
+}
+
 @end
 
 var CPTreeNodeRepresentedObjectKey  = @"CPTreeNodeRepresentedObjectKey",

Tests/AppKit/CPTreeNodeTest.j

@@ -0,0 +1,28 @@
+
+@import <AppKit/CPTreeNode.j>
+
+
+@implementation CPTreeNodeTest : OJTestCase
+{
+    CPTreeNode treeNode;
+    CPTreeNode childNode;
+}
+
+- (void)setUp
+{
+    treeNode = [CPTreeNode treeNodeWithRepresentedObject:nil];
+    
+    childNode = [CPTreeNode treeNodeWithRepresentedObject:nil];
+    [treeNode insertObject:childNode inChildNodesAtIndex:0];
+}
+
+- (void)testDescendantNodeAtIndexPath
+{
+    var indexPath = [CPIndexPath indexPathWithIndex:0];
+    [self assert:childNode equals:[treeNode descendantNodeAtIndexPath:indexPath]];
+    
+    indexPath = [CPIndexPath indexPathWithIndex:1];
+    [self assert:nil equals:[treeNode descendantNodeAtIndexPath:indexPath]];
+}
+
+@end