Improve error message from wrong test invocation
Improve error message from wrong test invocation

kimshrier/elixir,michalmuskala/elixir,elixir-lang/elixir,ggcampinho/elixir,kelvinst/elixir,ggcampinho/elixir,kimshrier/elixir,lexmag/elixir,pedrosnk/elixir,joshprice/elixir,lexmag/elixir,pedrosnk/elixir,kelvinst/elixir