Remove database_cleaner dependency in favor of Rails transactional sy…

…stem tests

spec/dummy/config/database.yml

@@ -6,7 +6,7 @@
 #
 default: &default
   adapter: sqlite3
-  pool: 5
+  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
   timeout: 5000
 
 development:

spec/dummy/config/puma.rb

@@ -1,47 +1,38 @@
-# Puma can serve each request in a thread from an internal thread pool.
-# The `threads` method setting takes two numbers a minimum and maximum.
-# Any libraries that use thread pools should be configured to match
-# the maximum value specified for Puma. Default is set to 5 threads for minimum
-# and maximum, this matches the default thread size of Active Record.
+# This configuration file will be evaluated by Puma. The top-level methods that
+# are invoked here are part of Puma's configuration DSL. For more information
+# about methods provided by the DSL, see https://puma.io/puma/Puma/DSL.html.
 #
-threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }.to_i
-threads threads_count, threads_count
-
-# Specifies the `port` that Puma will listen on to receive requests, default is 3000.
+# Puma starts a configurable number of processes (workers) and each process
+# serves each request in a thread from an internal thread pool.
 #
-port        ENV.fetch("PORT") { 3000 }
-
-# Specifies the `environment` that Puma will run in.
+# You can control the number of workers using ENV["WEB_CONCURRENCY"]. You
+# should only set this value when you want to run 2 or more workers. The
+# default is already 1.
 #
-environment ENV.fetch("RAILS_ENV") { "development" }
-
-# Specifies the number of `workers` to boot in clustered mode.
-# Workers are forked webserver processes. If using threads and workers together
-# the concurrency of the application would be max `threads` * `workers`.
-# Workers do not work on JRuby or Windows (both of which do not support
-# processes).
+# The ideal number of threads per worker depends both on how much time the
+# application spends waiting for IO operations and on how much you wish to
+# prioritize throughput over latency.
 #
-# workers ENV.fetch("WEB_CONCURRENCY") { 2 }
-
-# Use the `preload_app!` method when specifying a `workers` number.
-# This directive tells Puma to first boot the application and load code
-# before forking the application. This takes advantage of Copy On Write
-# process behavior so workers use less memory. If you use this option
-# you need to make sure to reconnect any threads in the `on_worker_boot`
-# block.
+# As a rule of thumb, increasing the number of threads will increase how much
+# traffic a given process can handle (throughput), but due to CRuby's
+# Global VM Lock (GVL) it has diminishing returns and will degrade the
+# response time (latency) of the application.
 #
-# preload_app!
-
-# The code in the `on_worker_boot` will be called if you are using
-# clustered mode by specifying a number of `workers`. After each worker
-# process is booted this block will be run, if you are using `preload_app!`
-# option you will want to use this block to reconnect to any threads
-# or connections that may have been created at application boot, Ruby
-# cannot share connections between processes.
+# The default is set to 3 threads as it's deemed a decent compromise between
+# throughput and latency for the average Rails application.
 #
-# on_worker_boot do
-#   ActiveRecord::Base.establish_connection if defined?(ActiveRecord)
-# end
+# Any libraries that use a connection pool or another resource pool should
+# be configured to provide at least as many connections as the number of
+# threads. This includes Active Record's `pool` parameter in `database.yml`.
+threads_count = ENV.fetch("RAILS_MAX_THREADS", 3)
+threads threads_count, threads_count
 
-# Allow puma to be restarted by `rails restart` command.
+# Specifies the `port` that Puma will listen on to receive requests; default is 3000.
+port ENV.fetch("PORT", 3000)
+
+# Allow puma to be restarted by `bin/rails restart` command.
 plugin :tmp_restart
+
+# Specify the PID file. Defaults to tmp/pids/server.pid in development.
+# In other environments, only set the PID file if requested.
+pidfile ENV["PIDFILE"] if ENV["PIDFILE"]

spec/spec_helper.rb

@@ -25,9 +25,9 @@
 ActiveRecord::Migrator.migrations_paths = [File.expand_path("../dummy/db/migrate", __FILE__)]
 ActiveRecord::Migration.maintain_test_schema!
 
-require 'database_cleaner'
-
 RSpec.configure do |config|
+  config.use_transactional_fixtures = true
+
   config.expect_with :rspec do |c|
     c.include_chain_clauses_in_custom_matcher_descriptions = true
   end

trestle.gemspec

@@ -27,6 +27,5 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "rspec-rails",         ">= 5.1.2"
   spec.add_development_dependency "rspec-html-matchers", "~> 0.10.0"
-  spec.add_development_dependency "database_cleaner",    "~> 2.1.0"
   spec.add_development_dependency "ammeter",             "~> 1.1.5"
 end