You need to always use braces for if() statements, although in this case the code above could be more easily written as:

```js
m.duration = 2000;
assert.strictEquals(m.duration, 2000);
m.duration = 10000;
assert.strictEquals(m.duration, 10000);
m.duration = NaN;
assert(isNan(m.duration), "isNan(m.duration)");
```

I also don't see any reason to test both 2000 and 10000.