Comparing code reviews against software testing is a bit odd to me. They are both necessary in a professional software environment.
Code reviews are great to ensure a consistent code base that follows a certain coding standard. It is also great for passing on the knowledge between developers (avoiding common pitfalls, better ways of doing things, etc...)
Testing is such a big field that it is hard to compare directly with reviewing code. Manual tests help in verifying the user experience and end to end scenarios, esp for UI (something that code reviews can't do). Automated functionality tests are great in verifying daily builds and catching regressions (which is also very hard to do in code reviews in fairly complicated systems). Various other types of automated tests are necessary for different considerations: performance tests, security tests etc...
The first paragraph of the article says exactly that: you need to invest in more than one of testing, reviews and QA, and different techniques may detect different types of errors.
Code reviews are great to ensure a consistent code base that follows a certain coding standard. It is also great for passing on the knowledge between developers (avoiding common pitfalls, better ways of doing things, etc...)
Testing is such a big field that it is hard to compare directly with reviewing code. Manual tests help in verifying the user experience and end to end scenarios, esp for UI (something that code reviews can't do). Automated functionality tests are great in verifying daily builds and catching regressions (which is also very hard to do in code reviews in fairly complicated systems). Various other types of automated tests are necessary for different considerations: performance tests, security tests etc...