Testing a databaseless Rails 5 application with rspec-rails

Question

I have a Rails 5.0.1 app that is NOT backed by any database. When attempting to write a controller test I get a ActiveRecord::ConnectionNotEstablished exception even though I have explicitly configured my spec/rails_helper.rb not to use ActiveRecord and removed references to active_record in config/application.rb. RSpec is trying to run such test within a transaction which requires a database connection to be established. I am attaching the stack trace for reference and I used this Github issue to setup RSpec without ActiveRecord rspec-rails for a rails project without db connection.

Failures:

1) ApplicationController the truth false not equal true Failure/Error: raise ConnectionNotEstablished, "No connection pool with id #{spec_name} found." unless pool

 ActiveRecord::ConnectionNotEstablished:
   No connection pool with id primary found.
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/activerecord-5.0.1/lib/active_record/connection_adapters/abstract/connection_pool.rb:882:in `retrieve_connection'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/activerecord-5.0.1/lib/active_record/connection_handling.rb:128:in `retrieve_connection'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/activerecord-5.0.1/lib/active_record/connection_handling.rb:91:in `connection'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/activerecord-5.0.1/lib/active_record/fixtures.rb:516:in `create_fixtures'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/activerecord-5.0.1/lib/active_record/fixtures.rb:1015:in `load_fixtures'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/activerecord-5.0.1/lib/active_record/fixtures.rb:988:in `setup_fixtures'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/activerecord-5.0.1/lib/active_record/fixtures.rb:852:in `before_setup'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-rails-3.6.1/lib/rspec/rails/adapters.rb:126:in `block (2 levels) in <module:MinitestLifecycleAdapter>'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example.rb:447:in `instance_exec'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example.rb:447:in `instance_exec'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/hooks.rb:375:in `execute_with'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/hooks.rb:606:in `block (2 levels) in run_around_example_hooks_for'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example.rb:342:in `call'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/hooks.rb:607:in `run_around_example_hooks_for'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/hooks.rb:464:in `run'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example.rb:457:in `with_around_example_hooks'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example.rb:500:in `with_around_and_singleton_context_hooks'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example.rb:251:in `run'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example_group.rb:627:in `block in run_examples'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example_group.rb:623:in `map'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example_group.rb:623:in `run_examples'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example_group.rb:589:in `run'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example_group.rb:590:in `block in run'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example_group.rb:590:in `map'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/example_group.rb:590:in `run'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:118:in `block (3 levels) in run_specs'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:118:in `map'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:118:in `block (2 levels) in run_specs'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/configuration.rb:1894:in `with_suite_hooks'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:113:in `block in run_specs'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/reporter.rb:79:in `report'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:112:in `run_specs'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:87:in `run'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:71:in `run'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/lib/rspec/core/runner.rb:45:in `invoke'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/gems/rspec-core-3.6.0/exe/rspec:4:in `<top (required)>'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/bin/rspec:23:in `load'
 # /home/vagrant/.bundle/easypost_admin/ruby/2.3.0/bin/rspec:23:in `<top (required)>'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/lib/bundler/cli/exec.rb:63:in `load'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/lib/bundler/cli/exec.rb:63:in `kernel_load'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/lib/bundler/cli/exec.rb:24:in `run'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/lib/bundler/cli.rb:304:in `exec'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/lib/bundler/vendor/thor/lib/thor/invocation.rb:126:in `invoke_command'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/lib/bundler/vendor/thor/lib/thor.rb:359:in `dispatch'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/lib/bundler/vendor/thor/lib/thor/base.rb:440:in `start'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/lib/bundler/cli.rb:11:in `start'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/exe/bundle:27:in `block in <top (required)>'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/lib/bundler/friendly_errors.rb:98:in `with_friendly_errors'
 # /opt/ruby2.3/lib64/ruby/gems/2.3.0/gems/bundler-1.12.5/exe/bundle:19:in `<top (required)>'
 # /vagrant/easypost_admin/vendor/bundle/bundle:23:in `load'
 # /vagrant/easypost_admin/vendor/bundle/bundle:23:in `<main>'
 #
 #   Showing full backtrace because every line was filtered out.
 #   See docs for RSpec::Configuration#backtrace_exclusion_patterns and
 #   RSpec::Configuration#backtrace_inclusion_patterns for more information.

Finished in 0.0058 seconds (files took 2.29 seconds to load) 1 example, 1 failure

Failed examples:

rspec ./spec/controllers/application_controller_spec.rb:15 # ApplicationController the truth false not equal true

UPDATE

rails_help.rb

require 'spec_helper'
ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)
# Prevent database truncation if the environment is production
abort("The Rails environment is running in production mode!") if Rails.env.production?
require 'rspec/rails'
# Add additional requires below this line. Rails is not loaded until this point!

# Checks for pending migration and applies them before tests are run.
# If you are not using ActiveRecord, you can remove this line.
# ActiveRecord::Migration.maintain_test_schema!

RSpec.configure do |config|
  # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
  # config.fixture_path = "#{::Rails.root}/spec/fixtures"

  # If you're not using ActiveRecord, or you'd prefer not to run each of your
  # examples within a transaction, remove the following line or assign false
  # instead of true.
  config.use_transactional_fixtures = false
  # The different available types are documented in the features, such as in
  # https://relishapp.com/rspec/rspec-rails/docs
  config.infer_spec_type_from_file_location!

  # Filter lines from Rails gems in backtraces.
  config.filter_rails_from_backtrace!
end

spec_helper.rb

RSpec.configure do |config|
  # rspec-expectations config goes here. You can use an alternate
  # assertion/expectation library such as wrong or the stdlib/minitest
  # assertions if you prefer.
  config.expect_with :rspec do |expectations|
    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
  end

  # rspec-mocks config goes here. You can use an alternate test double
  # library (such as bogus or mocha) by changing the `mock_with` option here.
  config.mock_with :rspec do |mocks|
    # Prevents you from mocking or stubbing a method that does not exist on
    # a real object. This is generally recommended, and will default to
    # `true` in RSpec 4.
    mocks.verify_partial_doubles = true
  end

  config.shared_context_metadata_behavior = :apply_to_host_groups
end

Answer 1

I had the very same issue with a rails 5.2.0.alpha app without a database configured. So I had a look at the rspec-rails code, and figured out this line which causes all the trouble:

rspec-rails/lib/rspec/rails/fixture_support.rb:

if defined?(ActiveRecord::TestFixtures)

It checks for a loaded ActiveRecord constant, which actually was loaded. I also had require 'active_record/railtie' commented out from config/application.rb. Then I figured out who required the ActiveStorage gem (bundle.lock). In my case it was ActiveStorage.

I just use the ActiveStorage functionality without a database, so I had to remove the ActiveRecord constant on my spec/rails_helper.rb:

# frozen_string_literal: true

# This file is copied to spec/ when you run 'rails generate rspec:install'
require 'spec_helper'
ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)

# Remove the ActiveRecord constant, because it is autloaded by
# ActiveStorage and not needed for our application. The presence
# of the ActiveRecord constant causes rspec-rails to include
# extra fixture support, which results in:
#
#   ActiveRecord::ConnectionNotEstablished:
#     No connection pool with 'primary' found.
#
Object.send(:remove_const, :ActiveRecord)

Mind the order, it needs to be placed after

require File.expand_path('../../config/environment', __FILE__)

and before

require 'rspec/rails'

This solution just modify the test environment.

UPDATE

I create an issue on rspec-rails which targets the creation of a global rspec configuration to turn off ActiveRecord handling.

Answer 2

A fix for this has just been merged into rspec-rails, and will supposedly be released along with RSpec Rails 4.0 sometimes next week.

What you have to set the following in your spec/rails_helper.rb:

config.use_active_record = false

Again, the problem is that if you didn't configure/use the database connection, but ActiveRecord is still present (due to Bundler loading it or some other reasons).