Practical Development
Real-world Elixir tooling and best practices -- Mix build tool, ExUnit testing, ExDoc documentation, error handling patterns, and file I/O for production projects.
Phase 4 is about shipping maintainable Elixir software with confidence. The focus shifts from language concepts to engineering discipline: project tooling, testing strategy, documentation quality, failure handling, and dependable I/O patterns. These lessons are designed to make your code easier to change, review, and operate.
This phase covers Mix in Depth, Testing with ExUnit, Documentation, Error Handling, and IO and File System.
Who this phase is for:
- Developers moving from tutorials to real project delivery.
- Teams that want predictable workflows for building, testing, and releasing Elixir code.
- Contributors who need stronger debugging and documentation practices.
What you should be able to do after this phase:
- Configure and use Mix tasks for daily development and automation.
- Write clear, maintainable ExUnit suites that catch regressions early.
- Produce useful module/function docs and doctests.
- Handle errors consistently with tuples, exceptions, and supervision-friendly boundaries.
- Use file and process I/O safely in command-line and service contexts.
Common pitfalls to watch for:
- Relying on only happy-path tests.
- Using exceptions for routine control flow.
- Writing docs after the fact instead of alongside behavior.
- Mixing side effects deeply into business logic.
Treat this phase as your “professional baseline.” If these practices become default habits, advanced architecture and operations work becomes far less risky.
An easy way to solidify this phase is to create a small sample project and apply every lesson to it: custom Mix aliases, full test coverage for key paths, module docs with doctests, and explicit error handling conventions. Reusable workflow habits are the real output of this phase.
Mix in Depth
Master Mix, Elixir's build tool -- create projects, manage Hex dependencies, write custom tasks, configure environments, and build production releases.
Testing with ExUnit
Write robust Elixir tests with ExUnit -- assertions, describe blocks, setup callbacks, async tests, doctests, tags, and mocking with Mox. Practical testing guide.
Documentation
Write excellent Elixir documentation with module attributes, doctests, typespecs, and ExDoc. Create self-verifying, publishable docs for your Hex packages.
Error Handling
Master Elixir error handling -- ok/error tuples, try/rescue, custom exceptions, the with statement, and the 'let it crash' approach used in OTP applications.
IO and File System
Read, write, and stream files in Elixir using the IO, File, Path, and System modules. Covers standard IO, file system navigation, and streaming large files.