Test when min == max

[Richienb]

(theoretically) If they are equal then the previous value will always be the same, so the program enters an infinite loop.

I think it is a better fix to make it work with only one number anyways, as opposed to throwing an error since this could happen if min and max are generated by another source.

[Richienb]

Nevermind, this issue is dealt with, but there are no tests.

unique-random/index.js

Line 9 in c1a6a94

previousValue = (number === previousValue && minimum !== maximum) ? random() : number;

[Richienb]

How bad is it that we're outputting the same number in a row in a package where we say that we don't do that?

[sindresorhus]

I would say that should be expected when only one number is possible, but I think we should document that just to cover our bases, and obviously add a test for it.