title: Heroku tests started failing overnight? (cannot configure sandbox)
body: <p>I’m getting a strange error when my tests run on Heroku which wasn’t happening on Friday, everything is fine locally.</p>
  
  <pre><code>-----&gt; Running test command `mix test`...
    08:29:52.761 [info] Already up
    08:29:53.389 [info] seeding in prod environment
    08:29:53.389 [info] runing default seeds
    All departments inserted
  
    ** (RuntimeError) cannot configure sandbox with pool DBConnection.Poolboy.
    To use the SQL Sandbox, configure your repository pool as:
    pool: Ecto.Adapters.SQL.Sandbox
    (ecto) lib/ecto/adapters/sql/sandbox.ex:429: Ecto.Adapters.SQL.Sandbox.mode/2
    (elixir) lib/code.ex:376: Code.require_file/2
    (elixir) lib/enum.ex:675: Enum."-each/2-lists^foreach/1-0-"/2
    (elixir) lib/enum.ex:675: Enum.each/2
    (mix) lib/mix/tasks/test.ex:229: Mix.Tasks.Test.run/1
  -----&gt; test command `mix test` failed with exit status 1
  </code></pre>
  
  <p>No changes to test config in months…</p>
  
  <pre><code># Configure your database
  config :ev2, Ev2.Repo,
    adapter: Ecto.Adapters.Postgres,
    username: "postgres",
    password: "postgres",
    database: "ev2_timecards_test",
    hostname: "localhost",
    pool: Ecto.Adapters.SQL.Sandbox
  </code></pre>
  
  <p><code>app.json</code> currently looks like this:</p>
  
  <pre><code>"environments": {
  "test": {
    "env": {
      "IS_STAGING": {
        "required": false
      }
    },
    "addons":[
      "heroku-postgresql:hobby-dev",
      "heroku-redis:hobby-dev"
    ],
    "scripts": {
      "test-setup": "mix ecto.migrate",
      "test": "mix test",
      "postdeploy": "bash &lt;(curl -s https://codecov.io/bash)"
    }
  }
  </code></pre>
  
  <p>}</p>
  
  <p>Running with Phoenix 1.3.</p>
  
  <p>I wonder if anyone is facing this on Monday morning or if anyone has any suggestions?</p>
  
  <p>Thanks in advance!</p>