Sample files for blog post "Simpler Elixir Travis Configuration" ... http://www.lee-dohm.com/2017/12/24/simpler-elixir-travis-configuration/

article-test.exs

use Mix.Config

# We don't run a server during test. If one is required,
# you can enable the server option below.
config :hello_phoenix, HelloPhoenix.Endpoint,
  http: [port: 4001],
  server: false

# Print only warnings and errors during test
config :logger, level: :warn

# Configure your database
config :hello_phoenix, HelloPhoenix.Repo,
  adapter: Ecto.Adapters.Postgres,
  username: "postgres",
  password: "postgres",
  database: "hello_phoenix_test",
  hostname: "localhost",
  pool: Ecto.Adapters.SQL.Sandbox

article-travis.exs

use Mix.Config

# We don't run a server during test. If one is required,
# you can enable the server option below.
config :hello_phoenix, HelloPhoenix.Endpoint,
  http: [port: 4001],
  server: false

# Print only warnings and errors during test
config :logger, level: :warn

# Configure your database
config :hello_phoenix, HelloPhoenix.Repo,
  adapter: Ecto.Adapters.Postgres,
  username: "postgres",
  password: "",
  database: "hello_phoenix_test",
  hostname: "localhost",
  pool: Ecto.Adapters.SQL.Sandbox

ci.exs

use Mix.Config

config :hello_phoenix, HelloPhoenix.Repo,
  password: ""

config.exs

use Mix.config

# Other configuration goes here

import_config "#{Mix.env}.exs"

test.exs

use Mix.Config

# We don't run a server during test. If one is required,
# you can enable the server option below.
config :hello_phoenix, HelloPhoenix.Endpoint,
  http: [port: 4001],
  server: false

# Print only warnings and errors during test
config :logger, level: :warn

# Configure your database
config :hello_phoenix, HelloPhoenix.Repo,
  adapter: Ecto.Adapters.Postgres,
  username: "postgres",
  password: "postgres",
  database: "hello_phoenix_test",
  hostname: "localhost",
  pool: Ecto.Adapters.SQL.Sandbox

# Customize the test environment for CI systems
if System.get_env("CI") == "true", do: import_config "ci.exs"