Well, first of all, such an unbiased test does not and probably cannot exist. People have to write the test, and despite their best efforts, they will likely still be biased. And how do you determine what 'unbiased' is in the first place? Such a test would likely give us the status quo or close to it because most hiring managers are acting in good faith already (at least, I chose to believe that people don't mean to perpetuate sexism/racism etc, they just aren't necessarily trying NOT to do it.)