I wonder if this test case could be more readable if we use the _.map along with _.each.

```javascript
_(["mp4", "webm", "ogg"]).map(function (ext) {
  return "video." + ext
}).each(function (filename) {
  ok(utils.isAVideo(filename), filename + "is recognized as a video")
  ok(utils.isAVideo("http://foo.bar/path/to/" + filename), filename + "is recognized as a video")
});
```

The assertion message repetition feels itchy.