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 when the corresponding Rails test classes already exist. If a suite uses LesliTesting::IntegrationTester, LesliTesting::ModelTester, or LesliTesting::ViewTester, load the Rails environment and rails/test_help before configuring LesliTesting:

ENV["RAILS_ENV"] ||= "test"
require_relative "../config/environment"
require "rails/test_help"

require "lesli_testing"
LesliTesting.app("MyApplication")

Rails autoloading means application models and controllers can still be covered when they are first referenced by tests. Code eagerly loaded before LesliTesting starts is not included in that process's coverage measurement.

Next steps

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Last Update: 2026/09/27