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Ensuring Elixir Application Performance with Testing and ExUnit

Testing Create Operation

Explore how to write tests for the create operation in Ecto queries using ExUnit. Understand how to verify successful data insertion and handle error scenarios effectively. Learn the importance of testing both return values and side effects to ensure data integrity in your Elixir applications.

We'll cover the following...

We’re going to start by looking at part of the logic file with our queries. The file, called Users, contains the basic CRUD actions:

  • create/1
  • get/1
  • update/2
  • delete/1

The file lib/users/users.ex in testing_ecto is provided:

create/1

The create/1 function in testing_ecto/lib/users/users.ex look like this:

Elixir
#file path -> testing_ecto/lib/users/users.ex
#add this code at the indicated place mentioned in comments of testing_ecto/lib/users/users.ex
#in the playground widget
  def create(params) do
    params
    |> User.create_changeset()
    |> Repo.insert()
  end

It’s pretty basic, as most CRUD queries are. As a result, testing it won’t be very complicated, either.

Writing tests

Let’s set up a new file at testing_ecto/test/users/users_test.ex.

Success path test

First, we’ll write a success path test.

In it, set up a basic test file structure and then add a describe block for create/1 and our first test:

Elixir
#file path -> testing_ecto/test/users/users_test.exs
#add this code at the indicated place mentioned in comments of testing_ecto/test/users/
#users_test.exs in the playground widget
  
  
  setup do
    Ecto.Adapters.SQL.Sandbox.checkout(TestingEcto.Repo) 
  end
  describe "create/1" do
    test "success: it inserts a user in the db and returns the user" do
      params = Factory.string_params_for(:user)  
      now = DateTime.utc_now()  
      assert {:ok, %User{} = returned_user} = Users.create(params)  
      user_from_db = Repo.get(User, returned_user.id)  
      assert returned_user == user_from_db  
      mutated = ["date_of_birth"]
      for {param_field, expected} <- params,
          param_field not in mutated do
        schema_field = String.to_existing_atom(param_field)
        actual = Map.get(user_from_db, schema_field)
        assert actual == expected,
               "Values did not match for field: #{param_field}\nexpected: #{
                 inspect(expected)
               }\nactual: #{inspect(actual)}"
      end
      expected_dob = Date.from_iso8601!(params["date_of_birth"])
      assert user_from_db.date_of_birth == expected_dob
      assert user_from_db.inserted_at == user_from_db.updated_at
      assert DateTime.compare(now, user_from_db.inserted_at) == :lt  
    end
  end

Let’s go through our test step-by-step:

  • Observe the common setup block at ...