Modify unit tests with more generation checks

lib/trie/trie.go

@@ -284,6 +284,8 @@ func (t *Trie) tryPut(key, value []byte) {
 // insert attempts to insert a key with value into the trie
 func (t *Trie) insert(parent Node, key []byte, value Node) Node {
 	newParent := t.maybeUpdateGeneration(parent)
+	value.SetGeneration(t.generation)
+
 	if newParent == nil {
 		value.SetKey(key)
 		return value
@@ -807,6 +809,8 @@ func handleDeletion(p *node.Branch, key []byte) Node {
 			for i, grandchild := range c.Children {
 				if grandchild != nil {
 					br.Children[i] = grandchild
+					// No need to copy and update the generation
+					// of the grand children since they are not modified.
 				}
 			}