Clear context variables as well

[yuya-takeyama]

And wrote usage with RSpec.

---

Testing

RSpec

It's recommended to clear state of Flagship before the suite and after the each tests.

You can do it by configuring like below:

RSpec.configure do |config|
  config.before(:suite) do
    Flagship.clear_state
  end

  config.after(:each) do
    Flagship.clear_state
  end
end