test: cover OrmPolymorphicTest and teardown

test/test_orm_polymorphic.rb

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+require 'minitest/autorun'
+require 'prism'
+require 'tmpdir'
+
+class OrmPolymorphicTest < Minitest::Test
+  def setup
+    @dir = Dir.mktmpdir('prism-polymorphic-store')
+    @store = CountingPolymorphicStore.new(File.join(@dir, 'test.pstore'))
+    @store.create_table(:posts, %w[id title])
+    @store.create_table(:photos, %w[id caption])
+    @store.create_table(:likes, %w[id likeable_id likeable_type user_id])
+    @store.create_table(:previews, %w[id previewable_id previewable_type url])
+
+    post_class = Class.new(Prism::Orm::Model) do
+      table_name :posts
+      has_many :likes, class_name: 'Like', as: :likeable, dependent: :destroy
+      has_one :preview, class_name: 'Preview', as: :previewable, dependent: :nullify
+    end
+    photo_class = Class.new(Prism::Orm::Model) do
+      table_name :photos
+      has_many :likes, class_name: 'Like', as: :likeable, dependent: :destroy
+    end
+    like_class = Class.new(Prism::Orm::Model) do
+      table_name :likes
+      belongs_to :likeable, polymorphic: true
+    end
+    preview_class = Class.new(Prism::Orm::Model) do
+      table_name :previews
+      belongs_to :previewable, polymorphic: true
+    end
+    [post_class, photo_class, like_class, preview_class].each { |klass| klass.store = @store }
+    Object.const_set(:Post, post_class)
+    Object.const_set(:Photo, photo_class)
+    Object.const_set(:Like, like_class)
+    Object.const_set(:Preview, preview_class)
+  end
+
+  def teardown
+    FileUtils.remove_entry(@dir)
+    %i[Post Photo Like Preview].each { |name| Object.send(:remove_const, name) if Object.const_defined?(name) }
+  end
+
+  def test_polymorphic_belongs_to_resolves_the_right_class
+    post = Post.create!(title: 'hello')
+    photo = Photo.create!(caption: 'sunset')
+    like_on_post = Like.create!(likeable_id: post.id, likeable_type: 'Post', user_id: 1)
+    like_on_photo = Like.create!(likeable_id: photo.id, likeable_type: 'Photo', user_id: 1)
+
+    assert_instance_of Post, like_on_post.likeable
+    assert_equal post.id, like_on_post.likeable.id
+    assert_instance_of Photo, like_on_photo.likeable
+    assert_equal photo.id, like_on_photo.likeable.id
+  end
+
+  def test_polymorphic_belongs_to_setter_stamps_both_columns
+    post = Post.create!(title: 'hello')
+    like = Like.new(user_id: 1)
+    like.likeable = post
+    like.save!
+
+    assert_equal post.id, like.likeable_id
+    assert_equal 'Post', like.likeable_type
+  end
+
+  def test_polymorphic_belongs_to_returns_nil_without_a_target
+    like = Like.create!(user_id: 1)
+    assert_nil like.likeable
+  end
+
+  def test_polymorphic_has_many_scopes_by_type_not_just_id
+    post = Post.create!(title: 'hello')
+    photo = Photo.create!(caption: 'sunset')
+    # Deliberately share the same numeric id across two different owner
+    # types - the whole point of the type column is that this must not
+    # cause cross-talk between Post#likes and Photo#likes.
+    Like.create!(likeable_id: post.id, likeable_type: 'Post', user_id: 1)
+    Like.create!(likeable_id: post.id, likeable_type: 'Photo', user_id: 2)
+
+    assert_equal 1, post.likes.count
+    assert_equal 1, post.likes.first.user_id
+  end
+
+  def test_polymorphic_has_many_dependent_destroy_only_removes_own_type
+    post = Post.create!(title: 'hello')
+    photo = Photo.create!(caption: 'sunset')
+    Like.create!(likeable_id: post.id, likeable_type: 'Post', user_id: 1)
+    Like.create!(likeable_id: photo.id, likeable_type: 'Photo', user_id: 1)
+
+    post.destroy
+
+    assert_equal 1, Like.all.count
+    assert_equal 'Photo', Like.all.first.likeable_type
+  end
+
+  def test_polymorphic_has_one_dependent_nullify_clears_both_columns
+    post = Post.create!(title: 'hello')
+    preview = Preview.create!(previewable_id: post.id, previewable_type: 'Post', url: '/p.png')
+
+    post.destroy
+
+    reloaded = Preview.find(preview.id)
+    assert_nil reloaded.previewable_id
+    assert_nil reloaded.previewable_type
+  end
+
+  def test_polymorphic_has_one_setter_stamps_both_columns
+    post = Post.create!(title: 'hello')
+    preview = Preview.create!(url: '/p.png')
+    post.preview = preview
+
+    reloaded = Preview.find(preview.id)
+    assert_equal post.id, reloaded.previewable_id
+    assert_equal 'Post', reloaded.previewable_type
+  end
+
+  def test_includes_polymorphic_belongs_to_batches_across_mixed_types
+    post = Post.create!(title: 'hello')
+    photo = Photo.create!(caption: 'sunset')
+    Like.create!(likeable_id: post.id, likeable_type: 'Post', user_id: 1)
+    Like.create!(likeable_id: photo.id, likeable_type: 'Photo', user_id: 2)
+    Like.create!(likeable_id: post.id, likeable_type: 'Post', user_id: 3)
+
+    @store.reset_query_count!
+    likes = Like.all.includes(:likeable).to_a
+    baseline = @store.query_count
+
+    targets = likes.map { |like| like.likeable.class.name }.sort
+    assert_equal baseline, @store.query_count,
+      "expected preloaded #likeable to be free, but it issued #{@store.query_count - baseline} more queries"
+    assert_equal %w[Photo Post Post], targets
+  end
+
+  def test_includes_polymorphic_has_many_avoids_n_plus_one_queries
+    3.times do |i|
+      post = Post.create!(title: "post#{i}")
+      2.times { |j| Like.create!(likeable_id: post.id, likeable_type: 'Post', user_id: j) }
+    end
+    Photo.create!(caption: 'unrelated')
+
+    @store.reset_query_count!
+    posts = Post.all.includes(:likes).to_a
+    baseline = @store.query_count
+
+    total = posts.sum { |post| post.likes.size }
+    assert_equal baseline, @store.query_count,
+      "expected preloaded #likes to be free, but it issued #{@store.query_count - baseline} more queries"
+    assert_equal 6, total
+  end
+end
+
+# Mirrors CountingStore/CountingThroughStore from the eager-loading tests -
+# a small local double so this file has no load-order dependency on them.
+class CountingPolymorphicStore < Prism::Orm::Store
+  def initialize(*)
+    super
+    @query_count = 0
+  end
+
+  attr_reader :query_count
+
+  def reset_query_count!
+    @query_count = 0
+  end
+
+  def all(table)
+    @query_count += 1
+    super
+  end
+
+  def find(table, id)
+    @query_count += 1
+    super
+  end
+end