Minitest::StubOnRoids

Provides a set of helper methods around Minitest's Object#stub method.

The following methods are available:

• .stub_with_args
  1. Stubs a class method for the duration of the block.
  2. If the method is called, asserts that it is called with the expected arguments.
  3. Doesn't mind how many times the method is called, if at all.
• .stub_and_expect
  1. Stubs a class method for the duration of the block.
  2. Asserts that the method is called the exact amount of times as expected, and with the expected arguments.

Installation

Add this line to your application's Gemfile:

gem "minitest-stub_on_roids"

And then execute:

$ bundle

Or install it yourself as:

$ gem install minitest-stub_on_roids

Usage

Require minitest/stub_on_roids in your test:

require 'minitest/stub_on_roids'

Extend the class you want to stub methods of:

Banana.extend Minitest::StubOnRoids

This will add the following methods to the class:

.stub_with_args

Use .stub_with_args to stub a class method as you normally would but also assert that if it is called - it is called with the expected arguments:

Banana.stub_with_args(:new, banana_mock, [3.0, "Yellow"]) do
  Banana.new(3.0, "Yellow")
end

# :new is stubbed and `banana_mock` is returned instead

Banana.stub_with_args(:new, banana_mock, [3.0, "Green"]) do
  Banana.new(3.0, "Yellow")
end

# A StubbedMethodArgsError is raised because :new was called with the wrong arguments

Just like with Minitest's Object#stub method, there is no expectation on the amount of times the stubbed method is called in the block.

.stub_and_expect

Use .stub_and_expect to stub a class method as you normally would but also set expectations on it, similarly to using Minitest::Mock#expect.

This means that a MockExpectationError will be raised if within the block...

• The method is called with a different set of arguments than expected.
• The method is called more or less the amount of times it was expected to be called.

Banana.stub_and_expect(:new, banana_mock, [3.0, "Yellow"]) do
  # Not calling `Banana.new`
end

# => MockExpectationError raised

Banana.stub_and_expect(:new, banana_mock, [3.0, "Yellow"]) do
  Banana.new(3.0, "Yellow")
  Banana.new(3.0, "Yellow")
end

# => MockExpectationError raised

Multiple calls

Use the times keyword argument to expect a method to be called multiple times within the block (default is 1):

Banana.stub_and_expect(:new, banana_mock, [3.0, "Yellow"], times: 2) do
  Banana.new(3.0, "Yellow")
  Banana.new(3.0, "Yellow")
end

# => Works

Multiple calls with different arguments

Use the expectations keyword argument to expect a method to be called a multiple times within the block with different arguments and return values (order must be respected).

Given the following expectations array:

expectations = [
  { 
    expected_args: [3.0, "Yellow"],
    return_value: banana_mock 
  },
  { 
    expected_args: [5.0, "Green"], 
    return_value: banana_mock2 
  },
  { 
    expected_args: [15.0, "Red"], 
    return_value: banana_mock3 
  }
]

Calling Banana.new multiple times exactly as expected works:

Banana.stub_and_expect(:new, expectations: expectations) do
  Banana.new(3.0, "Yellow")
  Banana.new(5.0, "Green")
  Banana.new(15.0, "Red")
end

# => Works

Calling Banana.new with the wrong arguments fails:

Banana.stub_and_expect(:new, expectations: expectations) do
  Banana.new(3.0, "Yellow")
  Banana.new(15.0, "Red")
end

# => MockExpectationError raised

Notes

• This gem might work with instance methods as well, but its intent is (and it's only tested for) using it on class methods.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/thatguysimon/minitest-stub_on_roids. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.