Change namespace from Cbra to Cobra

Considering your last commits, I changed all references from Cbratest to Cobratest

Used this little one liner to do the job

```bash
while read file; do sed -i '' 's/Cbra/Cobra/' $file; done < <(fgrep "Cbra" *|cut -d":" -f1|sort -d|uniq)
```

bonus: Fix the test without using allow_any_instance_of ;)