<NME> shims-test.js
<BEF> ADDFILE
<MSG> Add mocha ES6 shim.

<DFF> @@ -0,0 +1,8 @@
+import { describe, it } from 'mocha';
+
+describe('mocha-shim', function() {
+  it('should work', function() {
+    window.expect(describe).to.equal(window.describe);
+    window.expect(it).to.equal(window.it);
+  });
+});

Add mocha ES6 shim.