There may be other errata in the result of $ mix test test/doc_test.exs in page 177,
but at least:
6 tests, 1 failures 5 doctests, 1 failure
5, because the number of doctests is not changed from the previous page.
doctests, because ExUnit outputs test type, in this casedoctests, since Elixir 1.3.
failure, because it is singular (Elixir 1.1 and above).