My Erlang solution to the dev.to [Daily Challenge #19](https://dev.to/thepracticaldev/daily-challenge-19-turn-numbers-into-words-1bie).

The tests.txt file was generateg using the `num2en` function of the `Lingua::EN::Numbers` Perl module:

```perl
use Lingua::EN::Numbers qw{ num2en };

print $_, " ", num2en( $_ ), "\n" for 1 .. 999;
```

The Erlang unit tests load this file and generates a test per line.

To try:

```erl
% erl
1> c(words).
{ok,words}
2> words:test().
  All 1010 tests passed.
ok
3> words:test_words(51, 60).
  All 10 tests passed.
ok
```