Testing Fundamentals - Testing ActiveRecord

Exercise Questions
1

This topic is for the [Testing ActiveRecord] exercise in the [Testing Fundamentals] trail. Post any questions, corrections, or pointers you have to share with other Upcase subscribers.
[Testing ActiveRecord]: https://exercises.upcase.com/exercises/testing-fundamentals-testing-activerecord
[Testing Fundamentals]: Introduction to Ruby Tests | Learn RSpec | Testing Fundamentals

2

I cannot execute ‘rake spec’ on this exercise.

rake aborted!
NoMethodError: undefined method `last_comment' for #<Rake::Application:0x00000000a76638>
/home/chris/.rvm/gems/ruby-2.4.0/gems/rspec-core-3.1.4/lib/rspec/core/rake_task.rb:104:in `define'
/home/chris/.rvm/gems/ruby-2.4.0/gems/rspec-core-3.1.4/lib/rspec/core/rake_task.rb:80:in `initialize'
/home/chris/IdeaProjects/upcase/testing-fundamentals-testing-activerecord/Rakefile:5:in `new'
/home/chris/IdeaProjects/upcase/testing-fundamentals-testing-activerecord/Rakefile:5:in `<top (required)>'
/home/chris/.rvm/gems/ruby-2.4.0/gems/rake-12.1.0/exe/rake:27:in `<top (required)>'
/home/chris/.rvm/gems/ruby-2.4.0/bin/ruby_executable_hooks:15:in `eval'
/home/chris/.rvm/gems/ruby-2.4.0/bin/ruby_executable_hooks:15:in `<main>'
(See full trace by running task with --trace)

Using rake, version 12.1.0 in this project, and rake, version 10.3.2 in the ‘passing your first test’ project, which runs without errors. What can be the problem?