The Supreme Court has held that a particular IQ test had a disparate impact on black applicants. This makes IQ tests essentially radioactive for most corporations in the US.
1. That case was a social justice witch hunt. The purpose was to prove the political piety of the plaintiff.
2. The microscopic number of black engineers have already run the gamut of cognitive testing. An IQ test would not have a "disparate impact". This is why big corporations ask for university degrees: the degree itself is an IQ test.
3. FizzBuzz will screen out virtually the entire African race, and is provably related to actual job performance. After that an IQ test will not appreciably change the statistics.
As multi-racial fellow with an i.q. of 148 with out a university degree making six figures doing software development i'd like to say that I find #3 questionable.
http://en.wikipedia.org/wiki/Griggs_v._Duke_Power_Co.