It's hard until you have the toolchain and I/O working. That's what it's a test of. The rest of WebAssembly doesn't seem like an obstacle at all to me. For me the big unknown is how to get a wasm program running at all and communicating with something on my screen.

The idea is that it's the most basic example (in most instances) of ensuring your whole pipeline is setup correctly. It's the software equivalent of a smoke test.

It is a test that you can go from written code to an output that is human readable. This is the basic steps to allow us to use printf debugging. Until you get to this point, it can be hard to be sure your code is actually working or even compiling or if you have established a way to report errors.

As other poster's have commented, for most languages the code for this is trivial but the importance is that it tests the entire compile/link/execute tool chain which may not be as trivial to setup.