sass/sass-spec — pull request #76 by malrase (2014-10-07 18:13:59+00:00)
Title: Adding test case for sass/libsass#344 where interpolation doesn't work ...

...with negative numbers.

See issue here:
https://github.com/sass/libsass/issues/344

And breaking case here:
http://sassmeister.com/gist/f41fa16178103a7e0309