Grift

Mocking and spying in Ruby's MiniTest framework

Add this line to your application's Gemfile:

gem 'grift'

And then execute:

bundle install

Or install it yourself as:

gem install grift

We recommend using the plugin so that mocks are cleaned up after each test automatically. To enable the plugin, add the following lines of code to your test_helper file.

class Minitest::Test
  include Grift::MinitestPlugin
end

Or for Ruby on Rails:

class ActiveSupport::TestCase
  include Grift::MinitestPlugin
end

For complete usage guide, see the docs.

To "mock" a method and spy on its call args and results without changing the behavior of the method:

my_mock = Grift.spy_on(MyClass, :my_method)

To mock a method and its return value:

my_mock = Grift.mock(MyClass, :my_method, return_value)

my_spy = Grift.spy_on(MyClass, :my_method)
my_spy.mock_return_value(return_value)

To mock the implementation:

my_spy = Grift.spy_on(MyClass, :my_method)
my_spy.mock_implementation do |arg1, arg2|
    x = do_something(arg1, arg2)
    do_something_else(x) # the last line will be returned
end

or for a method taking keyword arguments:

my_spy = Grift.spy_on(MyClass, :my_method)
my_spy.mock_implementation do |arg1, arg2, **kwargs|
    x = do_something(arg1, arg2, kwargs[:arg3], kwargs[:arg4])
    do_something_else(x) # the last line will be returned
end

You can chain mock_return_value and mock_implementation after initializing the mock.

my_mock = Grift.spy_on(MyClass, :my_method).mock_implementation do |*args, **kwargs|
    do_something(*args, **kwargs)
end
#=> Grift::MockMethod object is returned

To get the results and details of the calls, call mock on your mock method object.

# get the number of times the mocked method has been called
my_mock.mock.count
#=> 2

# get args for each call to the method while mocked
my_mock.mock.calls[0].args
#=> ['first_arg1', 'second_arg1']

# get kwargs for each call to the method while mocked
my_mock.mock.calls[0].kwargs
#=> { first_arg1: 'value' }

# get results (return value) for each call to the method while mocked
my_mock.mock.results
#=> ['result1', 'result2']

Grift supports all Ruby versions >= 2.7 (including 3.3).

After forking the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

When developing, to install Grift whith your changes onto your local machine, run bundle exec rake install . For those with write access: to release a new version, update the version number in version.rb , and then run bundle exec rake release , which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

The docs are generated using YARD. To build the docs, first gem install yard . Then run yardoc to build the new docs. This is always done before a release to update the docs that get published and made available with the gem.

Bug reports and pull requests are welcome on GitHub at clarkedb/grift. Before submitting a pull request, see CONTRIBUTING.