Local Dependency Testing

The most powerful feature of livebook_test is the ability to test notebooks against your current codebase instead of published packages.

The Problem

Example notebooks in your repository typically reference your published Hex package:

Mix.install([
  {:my_lib, "~> 0.5"}
])

This works for end users, but creates a problem in CI: the notebook tests the published version of your code, not the current branch. Bugs in the current branch won't be caught by the notebook.

The Solution

livebook_test can automatically rewrite Mix.install dependencies to point to local paths:

mix livebook.test --mode local

This transforms:

Mix.install([{:my_lib, "~> 0.5"}])

into:

Mix.install([{:my_lib, path: "."}])

Now the notebook uses your current checkout.

Configuration

Via CLI

mix livebook.test --mode local

Via Application Config

# config/config.exs
config :livebook_test,
  dependency_mode: :local,
  local_deps: [
    my_lib: ".",
    other_lib: "../other_lib"
  ]

Programmatic

LivebookTest.run(mode: :local, local_deps: [my_lib: "."])

Multiple Dependencies

When your notebook depends on multiple packages from your organization:

Mix.install([
  {:ex_arrow, "~> 0.5"},
  {:ex_datalog, "~> 1.0"}
])

Configure each:

config :livebook_test,
  dependency_mode: :local,
  local_deps: [
    ex_arrow: ".",
    ex_datalog: "../ex_datalog"
  ]

Both dependencies will be rewritten to use local paths.

How It Works

The DependencyPatcher module uses regex-based replacement on the exported Elixir script (not the .livemd source). This means:

1. Your .livemd files remain unchanged - they still reference Hex versions
2. Only the temporary .exs scripts used for testing are patched
3. After the test run, the temporary scripts are deleted automatically

When to Use Remote vs Local

A good CI strategy: run both modes in separate jobs.

Next Steps

• CI/CD for Livebook Notebooks
• Executable Documentation