Mace (mace v0.1.0)

Per-test configuration isolation for ExUnit.

Provides set/3, set_many/2, get/3, reset/0, and diff/1 to manage test-scoped application config that intercepts Application.get_env transparently.

Setup

In test/test_helper.exs:

Mace.Store.init()
ExUnit.start()

Modules that need Application.get_env interception must also call Mace.Mock.install() in a setup_all block.

In your test module:

defmodule MyTest do
  use ExUnit.Case, async: true

  setup do
    Mace.set(:my_app, :timeout, 100)
    on_exit(fn -> Mace.reset() end)
    :ok
  end

  test "uses overridden timeout" do
    # Application.get_env(:my_app, :timeout) => 100
    assert MyModule.do_thing() == :ok
  end
end

Summary

Functions

cleanup(context)

Records the current process's config diffs and then resets. Call this in on_exit to enable automatic config-diff display on test failure.

diff(app)

Returns a formatted diff string comparing the current process's config overrides against the application defaults.

get(app, key)

Gets the active config override for the current process. Returns {:ok, value} or :error.

pid_config()

Returns the current pid's full config overrides as a nested map. Useful for debugging and for manual config transfer to spawned processes.

reset()

Clears all config overrides for the current test process. Call in on_exit to prevent config bleed.

set(app, kvlist)

Sets multiple config overrides from a keyword list.

set(app, key, value)

Sets a config override for the current test process.

task(fun)

Spawns a Task that inherits the current process's config overrides. Use instead of Task.async/1 when the spawned code calls Application.get_env.

Functions

cleanup(context)

Records the current process's config diffs and then resets. Call this in on_exit to enable automatic config-diff display on test failure.

Example

setup context do
  Mace.set(:my_app, :timeout, 100)
  on_exit(fn -> Mace.cleanup(context) end)
  :ok
end

diff(app)

Returns a formatted diff string comparing the current process's config overrides against the application defaults.

Returns empty string if no overrides or all overrides match defaults.

get(app, key)

Gets the active config override for the current process. Returns {:ok, value} or :error.

pid_config()

Returns the current pid's full config overrides as a nested map. Useful for debugging and for manual config transfer to spawned processes.

Example

config = Mace.pid_config()
# => %{my_app: %{timeout: 100, debug: true}}

reset()

Clears all config overrides for the current test process. Call in on_exit to prevent config bleed.

set(app, kvlist)

Sets multiple config overrides from a keyword list.

Example

Mace.set(:my_app, timeout: 100, debug: true)

set(app, key, value)

Sets a config override for the current test process.

Subsequent calls to Application.get_env(app, key) from the same process will return value instead of the real application config.

task(fun)

Spawns a Task that inherits the current process's config overrides. Use instead of Task.async/1 when the spawned code calls Application.get_env.

Example

task = Mace.task(fn -> MyModule.do_async_work() end)
result = Task.await(task)