diff -r efd9c589177a -r c0b4a8b5a012 toolkit/javascript/d3/test/core/transition-test-id.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/javascript/d3/test/core/transition-test-id.js	Thu Apr 10 14:20:23 2014 +0200
@@ -0,0 +1,20 @@
+require("../env");
+require("../../d3");
+
+var assert = require("assert");
+
+module.exports = {
+  topic: function() {
+    return d3.select("body").append("div").transition();
+  },
+  "has a positive integer id": function(transition) {
+    var id = transition.id;
+    assert.isTrue(id > 0);
+    assert.equal(~~id, id);
+  },
+  "increases monotonically across transitions": function(transition) {
+    var t0 = d3.select("body").append("div").transition(),
+        t1 = d3.select("body").append("div").transition();
+    assert.isTrue(t1.id > t0.id);
+  }
+};