As you might know, tuple call support was removed in OTP 21, so Ruby-like syntax expect(smth).to eq(smth_else) won’t work.

Version 1.6.0 allows you run ESpec with the new Erlang, but it doesn’t remove the old syntax completely, so you still can use it with older versions of OTP. But I recommend you to rewrite your tests using “pipe syntax”.

More details are here: https://github.com/antonmi/espec