Allow blacklisted names in tests

[mikeyhew]

Hi! First of all, great job with clippy to everyone involved. I just installed it and ran cargo clippy, and I like how seamlessly it runs – it's just like running cargo check, but with more lints.

One of the lints that I noticed is the lint for placeholder variable names like foo and bar. In general I think this is a great idea, but in the context of tests I think it should be turned off by default. I use foo and bar all the time in tests, and I don't think it's a problem there. Does anyone think otherwise?

[oli-obk]

Makes sense to me. Not sure how to solve it properly though. We can disable the lints via flags when cargo clippy is linting tests. For unit tests we'd need to add some way to prevent linting inside anything that has the #[test] attribute