You should be able to do this:

```javascript
TestsUtil.generateTestUsers(camAdminRestContext, 1, function(err, camUsers, camUser) {
    assert.ok(!err);
    TestsUtil.generateTestUsers(gtAdminRestContext, 1, function(err, gtUsers, gtUser) {
        assert.ok(!err);
```
`camUser` and `gtUser` are objects that each will have a `user` key and a `restContext` key that you can than use throughout your test. That way you don't need to manually create RestContexts (and it makes the tests a bit easier to read)