The slide where this comes up (~15:45) is about debugging. I think the point Rich is trying to make on that slide is that a bug in production passed the type checker and all the tests. Therefore, tests are not
solving the problem of building high quality systems.
Rather, tests (and type safety) are "guardrails" that warn when you when you are doing something wrong (they are reactive). As Rich said on Twitter (https://twitter.com/#!/richhickey/status/116490495500357633), "I have nothing against guard rails, but let's recognize their limited utility in trip planning and navigation."
I believe that linking back to the greater context, Rich is saying that simplicity and doing more to think about your problem at the beginning (proactive steps) provide value in building systems that are high quality and easy to maintain. I think he is at least implicitly challenging whether the value you get from simplicity is greater than the value you get from an extensive test suite.
I do not hear his comments as anti-testing, but rather more as pro-thinking and pro-simplicity. Personally, I find tests useful. I write them when writing Clojure code. However, I also get tremendous value from focusing on abstraction and composability and simplicity in design.