This is a good point. Random or not, a proper test set should have at least one test for each combination of input traits. Suppose the set of input traits is {hasHttp, hasHttps, hasWww, hasSLD, hasSubdomain, hasFilenameAtEnd}, where each trait is true or false. For all combinations of true and false values for those traits, the test set should include a URL that satisfies those traits.

Is it just me or does this function have a weird name? It returns true if you can make it to the next pump in time, right? But it's called zeroFuel. I'd expect it to return true if I ended up with zero fuel, not the opposite. Does that make sense?