Elixir: Access test helpers from dependency

In the java-world, artifacts for a specific library often come in two flavors, one with and one without test helpers. Is there an equivalent in the Elixir-world?

Specifically, I would like to be able to expose mocks or data generators in an application A. Application B now depends on A and gains the ability to use the exposed helpers from A in its own tests. Now, I do not want those helpers to appear anywhere in production, so they should only be included when specifically asked for (e.g. by MIX_ENV=test).