mSetup and mTeardown are supposed to be methods on `MockMessageManager`

Can I suggest that this becomes:

```js

MockMessageManager.sendSMS = function() {
  return {};
};

MockMessageManager.sendMMS = function() {
  return {};
};

MockMessageManager.mSetup = function() {
  sinon.spy(MockMessageManager, 'sendSMS');
  sinon.spy(MockMessageManager, 'sendSMS');
};

MockMessageManager.mTeardown = function() {
  MockMessageManager.sendSMS.restore();
  MockMessageManager.sendMMS.restore();
};
```

sinon offers the `.called` and will give you the arguments on `.args[callNumber][argNumber]`