Rails 5 beta bundle update has gem conflict - bundler

Question

I am trying to update Rails to 5.0.0.beta1, and I get errors that look like this:
Bundler could not find compatible versions for gem "minitest":
In Gemfile:
rails (= 5.0.0.beta1) was resolved to 5.0.0.beta1, which depends on
activejob (= 5.0.0.beta1) was resolved to 5.0.0.beta1, which depends on
activesupport (= 5.0.0.beta1) was resolved to 5.0.0.beta1, which depends
on minitest (~> 5.1)
minitest-rails-capybara was resolved to 0.0.1, which depends on
minitest-rails was resolved to 0.5, which depends on
minitest (~> 4.0)
No gem, including minitest-rails-capybara, has its version set explicitly in my Gemfile. There is no Gemfile.lock file in my app (I removed the existing one in the upgrade branch.)
minitest-rails-capybara is the latest version in the current gemset (and in others.) Why am I getting this error?
EDIT Even after starting with a new app, (rails new) if I add these lines to the Gemfile, I get the above errors:
group :test do
gem 'minitest-spec-rails'
gem 'minitest-rails-capybara'
end
Versions:
Ruby: 2.3.0
Bundler: 1.11.2
gem: 2.5.1

Answer 1

Well, I guess I'm jumping the gun somewhat here - those gems at least don't have their Rails5-compatible versions on Rubygems.org.
Pointing directly to Github fixes this:
gem 'minitest-rails', git: 'https://github.com/blowmage/minitest-rails', branch: 'rails5'
gem 'minitest-spec-rails'
gem 'minitest-rails-capybara', git: 'https://github.com/blowmage/minitest-rails-capybara', branch: 'rails5'