Add test environment

Rakefile

@@ -1,6 +1,13 @@
-require "bundler/gem_tasks"
+require "bundler/setup"
+Bundler::GemHelper.install_tasks
+
 require "rspec/core/rake_task"
 
-RSpec::Core::RakeTask.new(:spec)
+# Adds dummy:db tasks.
+load "spec/dummy/Rakefile"
 
-task default: :spec
+# Declares gem's own tasks.
+desc "Runs test suite."
+task default: %w(dummy:db:migrate) do
+  system "bundle exec rspec spec"
+end

lib/rspec/sqlimit.rb

@@ -1,11 +1,51 @@
 require "active_record"
 require "rspec"
 
-module RSpec::SQLimit
-  require_relative "sqlimit/counter"
-end
+module RSpec
+  module SQLimit
+    require_relative "sqlimit/counter"
+    require_relative "sqlimit/reporter"
+  end
+
+  Matchers.define :exceed_query_limit do |expected, matcher = nil|
+    def counter
+      @counter ||= RSpec::SQLimit::Counter.new
+    end
+
+    def message(expected, matcher, negation = false)
+      if matcher
+        condition   = negation ? "maximum" : "more than"
+        restriction = " that match #{matcher}"
+        suffix      = " among others (see mark ->)"
+      end
+
+      reporter = RSpec::SQLimit::Reporter.new(counter, matcher)
+
+      <<-MESSAGE.gsub(/ +\|/, "")
+        |Expected to run #{condition} #{expected} queries#{restriction}
+        |The following #{reporter.count} queries were invoked#{suffix}:
+        |#{reporter.lines.join("\n")}
+      MESSAGE
+    end
+
+    match do |block|
+      counter.count(&block)
+      RSpec::SQLimit::Reporter.new(counter, matcher).count > expected
+    end
+
+    match_when_negated do |block|
+      counter.count(&block)
+      RSpec::SQLimit::Reporter.new(counter, matcher).count <= expected
+    end
+
+    failure_message do |_|
+      message(expected, matcher)
+    end
+
+    failure_message_when_negated do |_|
+      message(expected, matcher, true)
+    end
 
-RSpec::Matchers.define :exceed_query_limit do
-  match do |block|
+    supports_block_expectations
   end
 end

lib/rspec/sqlimit/counter.rb

@@ -0,0 +1,26 @@
+module RSpec::SQLimit
+  class Counter
+    attr_reader :queries
+
+    def initialize
+      @queries = []
+    end
+
+    # FIXME add mutex to ensure thread-safety
+    def count
+      @queries = []
+      ActiveSupport::Notifications.subscribed(callback, "sql.active_record") do
+        yield
+      end
+    end
+
+    private
+
+    def callback
+      @callback ||= lambda(_name, start, finish, _message_id, values) do
+        return if %w(CACHE SCHEMA).include? values[:name]
+        queries << { sql: values[:sql], duration: (finish - start) * 1_000 }
+      end
+    end
+  end
+end

lib/rspec/sqlimit/reporter.rb

@@ -0,0 +1,30 @@
+module RSpec::SQLimit
+  class Reporter
+    attr_reader :matcher
+
+    def initialize(counter, matcher = nil)
+      @counter = counter
+      @matcher = matcher
+    end
+
+    def count
+      return queries.count unless @matcher
+      queries.count { |query| query[:sql] =~ @matcher }
+    end
+
+    def lines
+      queries.map.with_index { |*args| line(*args) }
+    end
+
+    private
+
+    def line(query, index)
+      prefix = @matcher && query =~ @matcher ? "->" : "  "
+      "#{prefix} #{index}) #{query[:sql]} (#{query[:duration].round(3)} ms)"
+    end
+
+    def queries
+      @queries ||= @counter.queries
+    end
+  end
+end

rspec-sqlimit.gemspec

@@ -13,9 +13,12 @@ Gem::Specification.new do |gem|
 
   gem.required_ruby_version = ">= 2.3"
 
-  gem.add_runtime_dependency "activerecord", "> 4.0", "< 6.0"
+  gem.add_runtime_dependency "rails", "> 4.0", "< 6.0"
   gem.add_runtime_dependency "rspec", "~> 3.0"
 
-  gem.add_development_dependency "rake"
+  gem.add_development_dependency "rspec", "~> 3.0"
+  gem.add_development_dependency "rake", "> 10.0"
+  gem.add_development_dependency "sqlite3", "~> 1.3"
+  gem.add_development_dependency "database_cleaner", "~> 1.5"
   gem.add_development_dependency "rubocop", "~> 0.44"
 end

spec/dummy/Rakefile

@@ -0,0 +1,14 @@
+require "active_record"
+require "bundler/setup"
+
+namespace :dummy do
+  task :environment do
+    require_relative "lib/dummy"
+  end
+
+  namespace :db do
+    task load_config: :environment
+  end
+
+  load "active_record/railties/databases.rake"
+end

spec/dummy/app/models/post.rb

@@ -0,0 +1,3 @@
+class Post < ActiveRecord::Base
+  belongs_to :user
+end

spec/dummy/app/models/user.rb

@@ -0,0 +1,3 @@
+class User < ActiveRecord::Base
+  has_many :posts
+end

spec/dummy/config/database.yml

@@ -0,0 +1,6 @@
+---
+test:
+  adapter:  :sqlite3
+  database: spec/dummy/db/test.sqlite3
+  pool:     5
+  timeout:  5000

spec/dummy/config/environment.rb

@@ -0,0 +1,10 @@
+Dummy::Application.configure do |config|
+  dummy        = File.expand_path "../..", __FILE__
+  database_yml = File.join(dummy, "config/database.yml")
+
+  config.database_configuration = YAML.load File.read(database_yml)
+  config.db_dir                 = File.join(dummy, "db")
+  config.env                    = :test
+  config.migrations_paths       = [File.join(dummy, "db/migrate")]
+  config.root                   = dummy
+end

spec/dummy/db/migrate/20170211104800_create_users.rb

@@ -0,0 +1,7 @@
+class CreateUsers < ActiveRecord::Migration
+  def change
+    create_table :users do |t|
+      t.string :name, index: true
+    end
+  end
+end

spec/dummy/db/migrate/20170211104823_create_posts.rb

@@ -0,0 +1,9 @@
+class CreatePosts < ActiveRecord::Migration
+  def change
+    create_table :posts do |t|
+      t.references :users
+      t.string     :title
+      t.text       :text
+    end
+  end
+end

spec/dummy/db/schema.rb

@@ -0,0 +1,26 @@
+# This file is auto-generated from the current state of the database. Instead
+# of editing this file, please use the migrations feature of Active Record to
+# incrementally modify your database, and then regenerate this schema definition.
+#
+# Note that this schema.rb definition is the authoritative source for your
+# database schema. If you need to create the application database on another
+# system, you should be using db:schema:load, not running all the migrations
+# from scratch. The latter is a flawed and unsustainable approach (the more migrations
+# you'll amass, the slower it'll run and the greater likelihood for issues).
+#
+# It's strongly recommended that you check this file into your version control system.
+
+ActiveRecord::Schema.define(version: 20170211104823) do
+
+  create_table "posts", force: :cascade do |t|
+    t.integer "users_id"
+    t.string  "title"
+    t.text    "text"
+  end
+
+  create_table "users", force: :cascade do |t|
+    t.string "name"
+    t.index ["name"], name: "index_users_on_name"
+  end
+
+end

spec/dummy/lib/dummy.rb

@@ -0,0 +1,9 @@
+require "active_record"
+require "bundler/setup"
+
+module Dummy
+  require_relative "dummy/application"
+  require_relative "../config/environment"
+  require_relative "../app/models/user.rb"
+  require_relative "../app/models/post.rb"
+end

spec/dummy/lib/dummy/application.rb

@@ -0,0 +1,26 @@
+module Dummy
+  class Application
+    class << self
+      # Configuration settings wrapper for the
+      # <tt>ActiveRecord::Tasks::DatabaseTasks</tt>.
+      #
+      # Establishes AR connection after configuration.
+      #
+      def configure
+        yield tasks
+        base.configurations = tasks.database_configuration
+        base.establish_connection(tasks.env)
+      end
+
+      private
+
+      def base
+        @base ||= ActiveRecord::Base
+      end
+
+      def tasks
+        @tasks ||= ActiveRecord::Tasks::DatabaseTasks
+      end
+    end
+  end
+end

spec/spec_helper.rb

@@ -1,8 +1,16 @@
 require "pry"
 require "rspec-sqlimit"
+require "database_cleaner"
+
+require_relative "dummy/lib/dummy"
+
+DatabaseCleaner.strategy = :truncation
 
 RSpec.configure do |config|
   config.order = :random
   config.filter_run focus: true
   config.run_all_when_everything_filtered = true
+
+  # Prepare the Test namespace for constants defined in specs
+  config.after(:each) { DatabaseCleaner.clean }
 end