The title is unfortunately more than a little irresponsible, considering it's the norm for many (most?) to read only the title.

There is no dichotomy here: you need to know testing as well as data structures and algorithms.

However, the thrust of the article itself I largely agree with -- that it's less important to have such in-depth knowledge about data structures and algorithms that you can implement them from scratch and from memory. Nearly any modern language you'll program in includes a standard library robust enough that you'll almost never have to implement many of the most well-known data structures and algorithms yourself. The caveat: you still need to know enough about how they work to be capable of selecting which to use.

In the off-chance you do have to implement something yourself, there's no shortage of reference material available.