When you publish a translation, it's better to leave a sugggestion in Discourse page to give it more visibility. If you want, let me know if you have other D translations pending so I can review them :) There are not many active users in this language.

You should add custom assertion messages to give a better feedback proving the input.

It's easy to do it with fluent asserts:

import std.string : format;
(...)
    functionName(input).should.equal(expected).because("input = %d".format(input));

To make things more handy, the best thing is to create a separate function that runs all the test, something like:

void dotest(uint seconds, string expected)
{
    humanreadable(seconds).should.equal(expected).because("seconds = %d".format(seconds));
}

Then you can use it for all the tests, fixed and random, just like this:

  dotest(seconds, expected);

Rejected because no random tests and author long time inactive.