Rather than using a mock expectation, I think you can do this:

``` ruby
expect {
  parser.parse([option])
}.to raise_error(SystemExit, /use --help.*#{option}/)
```

IMO, this is better because `abort` seems like an implementation detail (especially since you are not calling `abort`) and I generally prefer non-mock expectations for situations like this.

BTW, what is the full error message?