Flaky test

[bquorning]

From time to time I’ve seen the Rails 4.2 tests fail with a few (1-2) examples failing with NoMethodError: undefined method `mysql2_connection' for ActiveRecord::Base:Class. Re-running the test suite usually makes the test pass, and it makes me feel bad for it…

Example:

Database rake tasks::db:create#test_0001_creates the database and all shards:
NoMethodError: undefined method `mysql2_connection' for ActiveRecord::Base:Class
    /home/travis/build/zendesk/active_record_shards/gemfiles/vendor/bundle/ruby/2.4.0/gems/activerecord-4.2.9/lib/active_record/dynamic_matchers.rb:26:in `method_missing'
    /home/travis/build/zendesk/active_record_shards/lib/active_record_shards/tasks.rb:94:in `root_connection'
    /home/travis/build/zendesk/active_record_shards/lib/active_record_shards/tasks.rb:40:in `block (3 levels) in <top (required)>'
    /home/travis/build/zendesk/active_record_shards/lib/active_record_shards/tasks.rb:31:in `each'
    /home/travis/build/zendesk/active_record_shards/lib/active_record_shards/tasks.rb:31:in `block (2 levels) in <top (required)>'
    /home/travis/build/zendesk/active_record_shards/gemfiles/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `block in execute'
    /home/travis/build/zendesk/active_record_shards/gemfiles/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `each'
    /home/travis/build/zendesk/active_record_shards/gemfiles/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/task.rb:250:in `execute'
    /home/travis/build/zendesk/active_record_shards/gemfiles/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/task.rb:194:in `block in invoke_with_call_chain'
    /home/travis/.rvm/rubies/ruby-2.4.0/lib/ruby/2.4.0/monitor.rb:214:in `mon_synchronize'
    /home/travis/build/zendesk/active_record_shards/gemfiles/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/task.rb:187:in `invoke_with_call_chain'
    /home/travis/build/zendesk/active_record_shards/gemfiles/vendor/bundle/ruby/2.4.0/gems/rake-12.0.0/lib/rake/task.rb:180:in `invoke'
    /home/travis/build/zendesk/active_record_shards/test/helper.rb:75:in `rake'
    /home/travis/build/zendesk/active_record_shards/test/tasks_test.rb:42:in `block (3 levels) in <top (required)>'

cc @pschambacher @grosser