Yokai

Yokai is an alternative test runner for ExUnit based on file watcher. It watches for code changes and changes in selected test files to auto trigger a new test run with hot reloading, avoiding a cold start of the app/VM. The BEAM way.

Installation

Add yokai to your list of dependencies in mix.exs:

# You need this to make mix watch apply MIX_ENV=test for you.
def cli do
  [
    preferred_envs: [{:watch, :test}]
  ]
end

def deps do
  [
    {:yokai, "~> 0.3.0"}
  ]
end

Usage

# Run all tests and watch for changes
mix watch

# Run only this test file and watch for changes
mix watch test/module_name.exs

# Run all tests following a wildcard pattern
mix watch test/domain/*

# Increase the compile timeout for big projects
mix watch --compile-timeout 60

CLI Options

• --watch-folders (-w) - Comma-separated list of folders to watch for changes (default: "lib,test")
• --test-patterns (-t) - Comma-separated list of test patterns to run (default: "test/*/_test.exs")
• --compile-timeout (-c) - Compilation timeout in seconds (default: 30)

Examples

# Watch specific folders
mix watch --watch-folders lib,test,config

# Run specific test patterns
mix watch --test-patterns "test/unit/**/*_test.exs,test/integration/**/*_test.exs"

# Combine options
mix watch test/unit test/integration -w lib,test -c 45

Reason

The point is to have a faster iteration when developing tests/changes or applying TDD.

When talking about this idea it always comes up that you need to reload the environment when you change a config. To this there are 2 points against:

• Most of the time you are not changing configuration between runs, but when you do: mix test is still there, exactly the same.
• The hot reload from Phoenix is good enough for most apps and workflows. This applies the same rules but for tests.