ExUnitFixtures

A library for defining test fixtures for ExUnit tests. Inspired by py.test fixtures.

What are Fixtures?

Fixtures in ExUnitFixtures are just functions that will be run before a test. They can be used to setup the tests environment somehow, or provide the test with some data that it requires.

ExUnit provides the setup and setup_all functions that can be used for this. These work well for simpler cases, but have a couple of drawbacks:

• The setup code will run for all tests, even if the test does not need it.
• Sharing setup code between modules requires extracting it out into a function.

ExUnitFixtures attempts to solve that. It provides a way to define a fixture, which can be any bit of setup code that a test might require. Each of the tests in a file can then list the fixtures they require and have them injected into the tests context.

Installation

1. Add ex_unit_fixtures to your list of dependencies in mix.exs:

   def deps do
     [{:ex_unit_fixtures, "~> 0.1.0", only: [:test]}]
   end

Using ExUnit

For example, lets say some of your tests required a model named my_model, you need to define the fixture using deffixture and then tag your test to say it requires this fixture:

defmodule MyTests do
  use ExUnitFixtures
  use ExUnit.Case

  deffixture my_model do
    # Create a model somehow...
    %{test: 1}
  end

  @tag fixtures: [:my_model]
  test "that we have some fixtures", context do
    assert context.my_model.test == 1
  end
end

Fixtures with dependencies

Fixtures can also depend on other fixtures by naming a parameter after that fixture. For example, if you needed to setup a database instance before creating some models:

deffixture database do
  # set up the database somehow...
end

deffixture my_model(database) do
  # use the database to insert a model
end

@tag fixtures: [:my_model]
test "something" do
  # Test
end

In the sample above, we have 2 fixtures: one which creates the database and another which inserts a model into that database. The test function depends on my_model which depends on the database. ExUnitFixtures knows this, and takes care of setting up the database and passing it in to my_model.

Tearing down Fixtures

If you need to do some teardown work for a fixture you can use the ExUnit on_exit function:

defmodule TestWithTearDowns do
  use ExUnitFixtures
  use ExUnit.Case

  deffixture database do
    # Setup the database
    on_exit fn ->
      # Tear down the database
      nil
    end
  end
end