My migration does not appear to work. Why?

[jswanner]

@awerment

You will need to create a new migration with mix ecto.gen.migration add_url_to_testbeds and add the alter table(...) there, then run mix ecto.migrate again.

Expanding on that answer, the contents of the new migration file will look something like:

defmodule App.Repo.Migrations.AddUrlToTestbeds do
  use Ecto.Migration

  def change do
    alter table(:testbeds) do
      add :url, :string
    end
  end
end