fix a few edge cases in queue.pop()

Author: mourner

index.js

@@ -27,11 +27,14 @@ TinyQueue.prototype = {
     },
 
     pop: function () {
+        if (this.length === 0) return undefined;
         var top = this.data[0];
-        this.data[0] = this.data[this.length - 1];
         this.length--;
+        if (this.length > 0) {
+            this.data[0] = this.data[this.length];
+            this._down(0);
+        }
         this.data.pop();
-        this._down(0);
         return top;
     },
 

test.js

@@ -36,3 +36,20 @@ test('accepts data in constructor', function (t) {
 
     t.end();
 });
+
+test('handles edge cases with few elements', function (t) {
+    var queue = tinyQueue();
+
+    queue.push(2);
+    queue.push(1);
+    queue.pop();
+    queue.pop();
+    queue.pop();
+    queue.push(2);
+    queue.push(1);
+    t.equal(queue.pop(), 1);
+    t.equal(queue.pop(), 2);
+    t.equal(queue.pop(), undefined);
+
+    t.end();
+});