Add basic tests to help in gem maintenance

Author: Envek

.gitignore

@@ -7,3 +7,4 @@
 /pkg/
 /spec/reports/
 /tmp/
+.rspec_status

.ruby-version

@@ -1,10 +1,6 @@
 require 'bundler/gem_tasks'
-require 'rake/testtask'
+require 'rspec/core/rake_task'
 
-Rake::TestTask.new(:test) do |t|
-  t.libs << 'test'
-  t.libs << 'lib'
-  t.test_files = FileList['test/**/*_test.rb']
-end
+RSpec::Core::RakeTask.new
 
-task default: :test
+task default: :spec

Rakefile

@@ -27,8 +27,10 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency 'promise.rb', '~> 0.7'
 
   spec.add_development_dependency 'bundler', '~> 1.16'
-  spec.add_development_dependency 'minitest', '~> 5.0'
   spec.add_development_dependency 'pry', '~> 0.10'
   spec.add_development_dependency 'rake', '~> 10.0'
+  spec.add_development_dependency 'rspec', '~> 3.8'
+  spec.add_development_dependency 'rspec-sqlimit'
+  spec.add_development_dependency 'sqlite3'
   spec.add_development_dependency 'yard', '~> 0.9'
 end

graphql-preload.gemspec

@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+require "spec_helper"
+
+RSpec.describe GraphQL::Preload do
+  subject do
+    @result ||=
+      PreloadSchema.execute(query: query_string, context: {}, variables: {})
+  end
+
+  context "without associations" do
+    let(:query_string) { "query { products { title } }" }
+
+    it "doesn't load associations at all" do
+      expect { subject }.not_to exceed_query_limit 1
+    end
+  end
+
+  context "with associations" do
+    let(:query_string) do
+      <<~QRAPHQL
+        query { posts { title comments { text } } }
+      QRAPHQL
+    end
+
+    it "preloads associations by single query" do
+      expect { subject }.to exceed_query_limit 1 # to ensure that GraphQL query at least works
+      expect { subject }.not_to exceed_query_limit 2
+      posts = subject.dig("data", "posts")
+      expect(posts.size).to eq(4)
+      expect(posts.flat_map { |p| p["comments"] }.size).to eq(8)
+    end
+  end
+
+  context "with associations with custom scopes" do
+    let(:query_string) do
+      <<~QRAPHQL
+        query { users { name posts { title } } }
+      QRAPHQL
+    end
+
+    it "preloads associations by single query and given order" do
+      expect { subject }.not_to exceed_query_limit 2
+      posts = subject.dig("data", "users").flat_map { |p| p["posts"] }
+      # Posts for every user should be from greater rating to lower
+      expect(posts.map { |p| p["title"] }).to eq(%w[Bar Foo Baz Huh])
+    end
+  end
+end

spec/graphql/preload_spec.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+require "bundler/setup"
+require "graphql/preload"
+require "rspec-sqlimit"
+require "pry"
+
+require_relative "support/database"
+require_relative "support/graphql_schema"
+
+RSpec.configure do |config|
+  # Enable flags like --only-failures and --next-failure
+  config.example_status_persistence_file_path = ".rspec_status"
+
+  # Disable RSpec exposing methods globally on `Module` and `main`
+  config.disable_monkey_patching!
+
+  config.expect_with :rspec do |c|
+    c.syntax = :expect
+  end
+
+  config.mock_with :rspec
+
+  Kernel.srand config.seed
+  config.order = :random
+end

spec/spec_helper.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+require "active_record"
+require "sqlite3"
+
+ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
+
+ActiveRecord::Schema.define(version: 0) do
+  create_table :users do |t|
+    t.string :name
+  end
+
+  create_table :posts do |t|
+    t.string     :title
+    t.text       :text
+    t.float      :rating
+    t.references :author, foreign_key: { to_table: :users, column: :author_id, on_delete: :cascade }
+  end
+
+  create_table :comments do |t|
+    t.text       :text
+    t.references :post,   foreign_key: { on_delete: :cascade }
+    t.references :author, foreign_key: { to_table: :users, column: :author_id, on_delete: :cascade }
+  end
+end
+
+class User < ActiveRecord::Base
+  has_many :posts,    inverse_of: :author, foreign_key: :author_id
+  has_many :comments, inverse_of: :author, foreign_key: :author_id
+end
+
+class Post < ActiveRecord::Base
+  belongs_to :author, class_name: "User"
+  has_many :comments
+end
+
+class Comment < ActiveRecord::Base
+  belongs_to :author, class_name: "User"
+  belongs_to :post
+end
+
+alice, bob = User.create!([{ name: 'Alice' }, { name: 'Bob' }])
+
+alice.posts.create!([{ title: "Foo", rating: 4 }, { title: "Bar", rating: 8 }])
+bob.posts.create!([{ title: "Baz", rating: 7 }, { title: "Huh", rating: 4.2 }])
+
+Post.all.each do |post|
+  alice.comments.create(post: post, text: "Great post!")
+  bob.comments.create(post: post, text: "Great post!")
+end

spec/support/database.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+class CommentType < GraphQL::Schema::Object
+  field :id,        ID,     null: false
+  field :text,      String, null: false
+  field :author_id, ID,     null: false
+  field :post_id,   ID,     null: false
+end
+
+class PostType < GraphQL::Schema::Object
+  field :id,        ID,            null: false
+  field :title,     String,        null: false
+  field :text,      String,        null: false
+  field :rating,    Float,         null: false
+  field :comments,  [CommentType], null: false, preload: :comments
+  field :author_id, ID,            null: false
+end
+
+class UserType < GraphQL::Schema::Object
+  field :id,       ID,            null: false
+  field :name,    String,         null: false
+  field :comments, [CommentType], null: false, preload: :comments
+  field :posts,    [PostType],    null: false,
+                                  preload: :posts,
+                                  preload_scope: ->(*) { Post.order(rating: :desc) }
+end
+
+class QueryType < GraphQL::Schema::Object
+  field :users, [UserType], null: false
+  field :posts, [PostType], null: false
+
+  def users
+    User.all
+  end
+
+  def posts
+    Post.all
+  end
+end
+
+class PreloadSchema < GraphQL::Schema
+  use GraphQL::Batch
+  enable_preloading
+
+  query QueryType
+end