ExUnit: Passing context from one test to another?

Questions / Help
1

For example, I want to test an insert and an update to a database.

I need the database generated id from the result of the insert test to do the update test.

I see that ExUnit has setup methods that allow setting up a “context” that will be passed to tests.

However, is it possible to pass some results of one test to another test?

Also, and/or is it possible to do a setup between tests?

Example of what I’m talking about

What I’d like to do if tests could update the context for next tests:

defmodule InsertUpdateTest do
  use ExUnit.Case

  setup do
    # setup database stuff
  end

  test "insert works", _context do
    my_record = %{ name: "a record" }
    insert_result = InsertUpdate.insert( my_record )
    assert {:ok, %{ id: id} } = insert_result
    {:ok, %{ id: id } } # << context would be updated to include id
  end

  test "update works", context do
    %{id: id} = context # << getting the id from context that was set from the insert test
    # ... the rest of the test that uses the id for updating
  end
end

Another way if the above is not possible:

defmodule InsertUpdateTest do
  use ExUnit.Case

  setup do
    # setup database stuff
  end

  test "insert works", _context do
    my_record = %{ name: "a record" }
    insert_result = InsertUpdate.insert( my_record )
    assert {:ok, %{ id: id} } = insert_result
  end

  setup do
    # basically just do another insert since only(?) setup calls can change context
    my_record = %{ name: "a record" }
    {:ok, %{ id: id} } = InsertUpdate.insert( my_record )
    %{ id: id}  # << update context here using this id instead
  end

  test "update works", context do
    %{id: id} = context # << getting the id from context that was set from the setup method
    # ... the rest of the test that uses the id for updating
  end

  setup do
    # can I further change the context here so that the changes
    # apply only to "another test" below?
  end

  test "another test", context do
    # ...
  end
end
2

While it seems convenient to couple tests like this you should probably keep your tests self contained. Changing something in your insert test should not affect your update test.

3 Likes
3

Also tests should be running in parallel…

4

I see.

So, the best practice recommendation would be to separate the insert test and the update test into separate test cases (separate .exs files)?

5

Separate test cases yes, but no need to be in different .exs files.

1 Like
6

This is an old topic, but also something I wanted to do. I’d like to run some simple integration tests using Exunit. The first test would call an API to log a verification request. It would be nice to pass the verification ID it receives along to the following test, so it can be used in the next API call. I could combine it all in one test, but it looks a little ugly.

7

Instead of passing the ID from one test to the next test, create a setup helper, which fetches another ID independently as part of the second tests setup.

1 Like