config.exs

# This file is responsible for configuring your application
# and its dependencies with the aid of the Mix.Config module.
use Mix.Config

# This configuration is loaded before any dependency and is restricted
# to this project. If another project depends on this project, this
# file won't be loaded nor affect the parent project. For this reason,
# if you want to provide default values for your application for
# 3rd-party users, it should be done in your "mix.exs" file.

# You can configure for your application as:
#
#     config :cypher, key: :value
#
# And access this configuration in your application as:
#
#     Application.get_env(:cypher, :key)
#
# Or configure a 3rd-party app:
#
#     config :logger, level: :info
#

# It is also possible to import configuration files, relative to this
# directory. For example, you can emulate configuration per environment
# by uncommenting the line below and defining dev.exs, test.exs and such.
# Configuration from the imported file will override the ones defined
# here (which is why it is important to import them last).
#
#     import_config "#{Mix.env}.exs"

config :mix_test_watch, prefix: "iex -S mix"

mix.exs

defmodule Cypherex.Mixfile do
  use Mix.Project

  @version "0.0.1"
  @description "Cypher query language parsing library"
  @repo_url "https://github.com/johnhamelink/cyphex"

  def project do
    [app: :cypherex,
     name: "Cypherex",
     version: @version,
     elixir: "~> 1.1",
     description: @description,
     package: package,
     source_url: @repo_url,
     homepage_url: @repo_url,
     build_embedded: Mix.env == :prod,
     start_permanent: Mix.env == :prod,
     deps: deps,
     docs: [main: "README", extras: ["README.md"]]]
  end

  # Configuration for the OTP application
  #
  # Type "mix help compile.app" for more information
  def application do
    [applications: [:logger, :mix_test_watch]]
  end

  # Dependencies can be Hex packages:
  #
  #   {:mydep, "~> 0.3.0"}
  #
  # Or git/path repositories:
  #
  #   {:mydep, git: "https://github.com/elixir-lang/mydep.git", tag: "0.1.0"}
  #
  # Type "mix help deps" for more examples and options
  defp deps do
    [
      {:mix_test_watch, github: "lpil/mix-test.watch", only: :dev},
      {:ex_spec, "~> 1.0.0", only: :test},
      {:inch_ex, only: :docs},
      {:earmark, "~> 0.1", only: :dev},
      {:ex_doc, "~> 0.11", only: :dev}
    ]
  end

  defp package do
    [maintainers: ["John Hamelink"],
     licenses: ["MIT"],
     links: %{"GitHub" => @repo_url},
     files: ~w(lib src/*.xrl src/*.yrl mix.exs *.md LICENSE)]
  end
end

Output

2z [john:~/Public/cypher] master(+7/-3) ± mix test.watch

Running tests...

=INFO REPORT==== 5-Dec-2015::23:07:54 ===
    application: logger
    exited: stopped
    type: temporary
** (Mix) Could not start application mix_test_watch: could not find application file: mix_test_watch.app