lcov reporter is not working

I'm trying to use the lvoc reporter on my project, but there's just no output from nodeunit.

If I invoke nodeunit test only:

```
henvic at henvic-mp in ~/projects/liferay/grunt-cli-config (master●●)
$ nodeunit test

config_options_test
✔ config_options - normalize
✔ config_options - parse
✔ config_options - any
✔ config_options - boolean
✔ config_options - negative

OK: 5 assertions (140ms)
```

If I try to invoke with the lcov reporter:

```
henvic at henvic-mp in ~/projects/liferay/grunt-cli-config (master●●)
$ nodeunit test --reporter lcov
```

If I try to invoke with the html reporter:

```
henvic at henvic-mp in ~/projects/liferay/grunt-cli-config (master●●)
$ nodeunit test --reporter=html

body { font: 12px Helvetica Neue }
h2 { margin:0 ; padding:0 }
pre { font: 11px Andale Mono; margin-left: 1em; padding-left: 1em; margin-top:0; font-size:smaller;}
.assertion_message { margin-left: 1em; }
ol { list-style: none; margin-left: 1em; padding-left: 1em; text-indent: -1em;}
ol li.pass:before { content: "\2714 \0020"; }
ol li.fail:before { content: "\2716 \0020"; }

config_options_test

1. config_options - normalize


2. config_options - parse


3. config_options - any


4. config_options - boolean


5. config_options - negative

OK: 5 assertions (151ms)

```

nodeunit version 0.8.6, node.js version 0.10.26.
Repo https://github.com/henvic/grunt-cli-config