Ensuring Elixir Application Performance with Testing and ExUnit/

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Testing Update Operation

Testing Update Operation

Learn how to test Update operation in Elixir.

We'll cover the following...

Testing update is a combination of the testing for the create and read functions.

The Update function

Let’s first look at the function we’re going to test:

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#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 update(%User{} = existing_user, update_params) do
  existing_user
  |> User.update_changeset(update_params)
  |> Repo.update()
end

Like create/1, we can see that this function is a very lightweight wrapper around calls to the schema’s changeset function (update_changeset/2 in this case) and then to Repo.update/1.

Tests

Testing the update function will be similar, but we’ll need to insert an existing user to be updated by the code.

Let’s write our success test first:

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#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
  test "success: it updates database and returns the user" do
    existing_user = Factory.insert(:user) 
    params =  
      Factory.string_params_for(:user)
      |> Map.take(["first_name"])
    assert {:ok, returned_user} = Users.update(existing_user, params)
    user_from_db = Repo.get(User, returned_user.id)
    assert returned_user == user_from_db
    expected_user_data =  
      existing_user
      |> Map.from_struct()
      |> Map.drop([:__meta__, :updated_at])  
      |> Map.put(:first_name, params["first_name"])
    for {field, expected} <- expected_user_data do
      actual = Map.get(user_from_db, field)
      assert actual == expected,
              "Values did not match for field: #{field}\nexpected: #{
                inspect(expected)
              }\nactual: #{inspect(actual)}"
    end
    refute user_from_db.updated_at == existing_user.updated_at  
    assert %DateTime{} = user_from_db.updated_at
  end

Let’s take a look at this test:

  • The test uses the factory to insert a user in line 6.
  • In the instruction starting from line 8, the test is creating a
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