Elixir Postgres view returning empty dataset when testing - postgresql

Question

I am trying to test a view created in Postgres, but it is returning an empty result set. However, when testing out the view in an Elixir interactive shell, I get back the expected data. Here are the steps I have taken to create and test the view:
Create a migration:
def up do
execute """
CREATE VIEW example_view AS
...
Create the schema:
import Ecto.Changeset
schema "test_view" do
field(:user_id, :string)
Test:
describe "example loads" do
setup [
:with_example_data
]
test "view" do
query = from(ev in Schema.ExampleView)
IO.inspect Repo.all(query)
end
end
The response back is an empty array []
Is there a setting that I am missing to allow for views to be tested in test?

Answer 1

As pointed out in one of the comments:
iex, mix phx.server... run on the :dev environment and the dev DB
tests use the :test environment and runs on a separate DB
It actually makes a lot of sense because you want your test suite to be reproducible and independent of whatever records that you might create/edit in your dev env.
You can open iex in the :test environment to confirm that your query returns the empty array here too:
MIX_ENV=test iex -S mix
What you'll need is to populate your test DB with some known records before querying. There are at least 2 ways to achieve that: fixtures and seeds.
Fixtures:
define some helper functions to create records in test/support/test_helpers.ex (typically: takes some attrs, adds some defaults and calls some create_ function from your context)
def foo_fixture(attrs \\ %{}) do
{:ok, foo} =
attrs
|> Enum.into(%{name: "foo", bar: " default bar"})
|> MyContext.create_foo()
foo
end
call them within your setup function or test case before querying
side note: you should use DataCase for tests involving the DB. With DataCase, each test is wrapped in its own transaction and any fixture that you created will be rollback-ed at the end of the test, so tests are isolated and independent from each other.
Seeds:
If you want to include some "long-lasting" records as part of your "default state" (e.g. for a list of countries, categories...), you could define some seeds in priv/repo/seeds.exs.
The file should have been created by the phoenix generator and indicate you how to add seeds (typically use Repo.insert!/1)
By default, mix will run those seeds whenever you run mix ecto.setup or mix ecto.reset just after your migrations (whatever the env used)
To apply any changes in seeds.exs, you can run the following:
# reset dev DB
mix ecto.reset
# reset test DB
MIX_ENV=test mix ecto.reset
If you need some seeds to be environment specific, you can always introduce different seed files (e.g. dev_seeds.exs) and modify your mix.exs to configure ecto.setup.
Seeds can be very helpful not only for tests but for dev/staging in the early stage of a project, while you are still tinkering a lot with your schema and you are dropping the DB frequently.
I usually find myself using a mix of both approaches.