elixir mock inner function url request

Question

How could I mock a specific api call similar to how python requests-mock works:

with requests_mock.mock() as m:
    m.get('http://test.com', text='data')
    requests.get('http://test.com').text

In this example every call to http://test.com inside the with statement will be mocked

So in elixir, for example, I have this:

defmodule API do

  # makes a call to an external API I dont want to test
  def make_call do
    ...
  end
end

defmodule Item do

  alias API

  # function I actually want to test
  def build_request do
    API.make_call
    # stuff I want to test
  end

end

So let's say I want to test build_request mocking make_call

I tried this package https://github.com/jjh42/mock but what this package does is to override whole API module with for example a mock for make_call method but you also lose all the other functions of the API module and I dont want that.

How could I mock that call?

Here in another example I saw https://hashrocket.com/blog/posts/mocking-api-s-with-elixir

# mocking a github api call directly
@github_api.make_request(:get, "/users/#{username}")

But it's the same issue, it mocks the request straight in the test, my issue is when the mock needs to be done in an inner function not straight away.

Aleksei Matiushkin Aleksei Matiushkin · Accepted Answer · 2018-04-02T08:59:55

Dependency injection is your friend:

def build_request(caller \\ API) do
  caller.make_call
  # stuff I want to test
end

And in tests you supply a parameter to the call to build_request:

build_request(TestAPI)

For the details please refer to this brilliant writing by José Valim.

elixir mock inner function url request

1 Answers