You never define Helper
in test.js
—only helper
on this line:
var helper = require('../src/js/helper.js');
Use the lower case helper
that you defined.
By the way, you might want to change your exports line in helper.js
from this:
exports.helper = Helper;
To this:
exports.Helper = Helper;
Then use helper in test.js
like so:
assert.equal(1501, (new helper.Helper()).parseValue('1d 1h 1m', 'when'));
Or just do something like this:
var Helper = require('../src/js/helper.js').Helper;