Installation and configuration

Install the gem

Add LesliTesting to the test group of a Rails application, Rails engine, or Ruby gem:

bundle add lesli_testing --group test

The equivalent Gemfile entry is:

group :test do
  gem "lesli_testing"
end

When the dependency is declared in a gemspec, keep it as a development dependency because applications using the released gem do not need LesliTesting at runtime:

spec.add_development_dependency "lesli_testing"

For local development inside a Lesli workspace, point Bundler to the checkout:

group :test do
  gem "lesli_testing", path: "gems/LesliTesting"
end

Then install the dependencies:

bundle install

Select a project profile

Require LesliTesting in test/test_helper.rb and call one configuration method:

require "lesli_testing"

LesliTesting.app("LesliBuilder")

Available methods are:

Method	Intended project	Coverage profile
`LesliTesting.app(name, options = {})`	Rails application	Tracks Ruby files in `app`, `lib`, `engines`, and `gems`.
`LesliTesting.engine(name, options = {})`	Rails engine	Uses the Rails profile and filters test files.
`LesliTesting.gem(name, options = {})`	Standalone Ruby gem	Tracks the standard `app` and `lib` paths and filters test files.

Do not call more than one profile method in the same test process. All three methods configure the same global Minitest and SimpleCov instances.

Configuration options

Pass options as keyword-style hash entries:

LesliTesting.engine(
  "LesliShield",
  coverage_missing_len: 30,
  coverage_min_coverage: 80
)

Option	Type	Default	Description
`coverage_missing_len`	Integer	`25`	Maximum number of characters displayed for missing lines in console coverage output. Use `0` for no limit.
`coverage_min_coverage`	Numeric	`90`	Minimum required line-coverage percentage. A coverage run fails below this value.

The selected project profile is set internally. Applications should not pass coverage_profile directly.

Load order

Coverage must start before the files being measured are required. Put the LesliTesting configuration as early as the test environment permits:

require "lesli_testing"
LesliTesting.gem("MyGem")

require "minitest/autorun"
require "my_gem"

Rails-only base classes are created through ActiveSupport load hooks. Configure LesliTesting before booting Rails; the shared classes and helpers are created when rails/test_help loads their corresponding Rails test classes:

ENV["RAILS_ENV"] ||= "test"
require "lesli_testing"
LesliTesting.app("MyApplication")

require_relative "../config/environment"
require "rails/test_help"

LesliTesting can still be required by a standalone Ruby gem without Rails. Rails-only files and test classes are optional in that mode.

Rails engines should use the setup and Rails runner commands documented in Testing Rails engines. Do not execute an engine test file directly with Ruby when it inherits from a shared LesliTesting Rails class.

This order lets coverage observe application boot code while keeping Rails-specific test classes deferred until the Rails testing framework is ready.

See Load order and process behavior for the complete initialization lifecycle, environment variables, and exit-code contract.

Next steps

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Last Update: 2026/10/20