diff --git a/types/bintrees/bintrees-tests.ts b/types/bintrees/bintrees-tests.ts
index fa03ae5941..fb4a22a3d8 100644
--- a/types/bintrees/bintrees-tests.ts
+++ b/types/bintrees/bintrees-tests.ts
@@ -1,16 +1,50 @@
+/// <reference types="mocha" />
+/// <reference types="node" />
+import assert = require('assert');
 import { BinTree, RBTree } from 'bintrees';
 
-let treeA = new RBTree((a:number, b:number) => a - b);
+describe('bintrees', () => {
+    it('builds a simple tree', () => {
+        let treeA = new RBTree((a: number, b: number) => a - b);
 
-treeA.insert(5);
-treeA.insert(3);
+        treeA.insert(5);
+        treeA.insert(3);
+        treeA.remove(3);
 
-let treeB = new BinTree((a:string, b:string) => a.length - b.length);
+        assert.equal(treeA.size, 1);
+    });
 
-treeB.insert('hi');
-treeB.insert('there');
-treeB.insert('how');
-treeB.insert('are');
+    it('builds a tree of strings', () => {
+        let treeB = new BinTree((a:string, b:string) => a.length - b.length);
 
-treeB.remove('how');
+        treeB.insert('hi');
+        treeB.insert('there');
+        treeB.insert('how');
+        treeB.insert('are'); // ignored
+        treeB.remove('how');
+
+        assert.equal(treeB.size, 2);
+        assert.equal(treeB.min(), 'hi');
+    });
+
+    it('maintains a tree of objects', () => {
+
+        interface C {
+            id: number
+        }
+
+        let treeC = new BinTree<C>((a: C, b: C) => a.id - b.id);
+
+        treeC.insert({ id: 100 });
+        treeC.insert({ id: 110 });
+        treeC.insert({ id: 105 });
+
+        let ids: number[] = [];
+        treeC.each((val: C) => {
+            ids.push(val.id);
+        });
+
+        assert.deepEqual(ids, [100, 105, 110]);
+    });
+});