test: cover OrmHasManyThroughTest and teardown

test/test_orm_has_many_through.rb

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+require 'minitest/autorun'
+require 'prism'
+require 'tmpdir'
+
+class OrmHasManyThroughTest < Minitest::Test
+  def setup
+    @dir = Dir.mktmpdir('prism-through-store')
+    @store = CountingThroughStore.new(File.join(@dir, 'test.pstore'))
+    @store.create_table(:posts, %w[id title])
+    @store.create_table(:commenters, %w[id name])
+    @store.create_table(:comments, %w[id post_id commenter_id body])
+
+    post_class = Class.new(Prism::Orm::Model) do
+      table_name :posts
+      has_many :comments, class_name: 'Comment', foreign_key: 'post_id', dependent: :destroy
+      has_many :commenters, through: :comments, source: :commenter
+    end
+    commenter_class = Class.new(Prism::Orm::Model) do
+      table_name :commenters
+      has_many :comments, class_name: 'Comment', foreign_key: 'commenter_id'
+      has_many :posts, through: :comments, source: :post
+    end
+    comment_class = Class.new(Prism::Orm::Model) do
+      table_name :comments
+      belongs_to :post, class_name: 'Post', foreign_key: 'post_id'
+      belongs_to :commenter, class_name: 'Commenter', foreign_key: 'commenter_id'
+    end
+    [post_class, commenter_class, comment_class].each { |klass| klass.store = @store }
+    Object.const_set(:Post, post_class)
+    Object.const_set(:Commenter, commenter_class)
+    Object.const_set(:Comment, comment_class)
+  end
+
+  def teardown
+    FileUtils.remove_entry(@dir)
+    %i[Post Commenter Comment].each { |name| Object.send(:remove_const, name) if Object.const_defined?(name) }
+  end
+
+  def test_has_many_through_collects_source_records
+    post = Post.create!(title: 'hello world')
+    alice = Commenter.create!(name: 'alice')
+    bob = Commenter.create!(name: 'bob')
+    Comment.create!(post_id: post.id, commenter_id: alice.id, body: 'nice')
+    Comment.create!(post_id: post.id, commenter_id: bob.id, body: 'agreed')
+
+    names = post.commenters.map(&:name).sort
+    assert_equal %w[alice bob], names
+  end
+
+  def test_has_many_through_dedupes_by_id
+    post = Post.create!(title: 'hello world')
+    alice = Commenter.create!(name: 'alice')
+    Comment.create!(post_id: post.id, commenter_id: alice.id, body: 'first')
+    Comment.create!(post_id: post.id, commenter_id: alice.id, body: 'second')
+
+    assert_equal [alice.id], post.commenters.map(&:id)
+  end
+
+  def test_has_many_through_is_symmetric_from_the_other_side
+    post = Post.create!(title: 'hello world')
+    alice = Commenter.create!(name: 'alice')
+    Comment.create!(post_id: post.id, commenter_id: alice.id, body: 'first')
+
+    assert_equal [post.id], alice.posts.map(&:id)
+  end
+
+  def test_has_many_through_returns_empty_array_without_through_records
+    post = Post.create!(title: 'lonely')
+    assert_equal [], post.commenters
+  end
+
+  def test_has_many_through_default_source_is_singularized_name
+    post_class = Class.new(Prism::Orm::Model) do
+      table_name :posts
+      has_many :comments, class_name: 'Comment', foreign_key: 'post_id'
+      has_many :commenters, through: :comments
+    end
+    post_class.store = @store
+    post = post_class.create!(title: 'defaults')
+    alice = Commenter.create!(name: 'alice')
+    Comment.create!(post_id: post.id, commenter_id: alice.id, body: 'default source')
+
+    assert_equal ['alice'], post_class.find(post.id).commenters.map(&:name)
+  end
+
+  def test_has_many_through_rejects_dependent_option
+    error = assert_raises(ArgumentError) do
+      Class.new(Prism::Orm::Model) do
+        table_name :posts
+        has_many :comments, class_name: 'Comment', foreign_key: 'post_id'
+        has_many :commenters, through: :comments, source: :commenter, dependent: :destroy
+      end
+    end
+    assert_match(/dependent/, error.message)
+  end
+
+  def test_includes_has_many_through_avoids_n_plus_one_queries
+    3.times do |i|
+      post = Post.create!(title: "post#{i}")
+      2.times do |j|
+        commenter = Commenter.create!(name: "commenter#{i}-#{j}")
+        Comment.create!(post_id: post.id, commenter_id: commenter.id, body: 'hi')
+      end
+    end
+
+    @store.reset_query_count!
+    posts = Post.all.includes(:commenters).to_a
+    baseline = @store.query_count
+
+    total = posts.sum { |post| post.commenters.size }
+    assert_equal baseline, @store.query_count,
+      "expected preloaded #commenters to be free, but it issued #{@store.query_count - baseline} more queries"
+    assert_equal 6, total
+  end
+
+  def test_includes_has_many_through_unknown_through_raises
+    broken_class = Class.new(Prism::Orm::Model) do
+      table_name :posts
+      has_many :commenters, through: :nonexistent, source: :commenter
+    end
+    broken_class.store = @store
+    broken_class.create!(title: 'x')
+    assert_raises(ArgumentError) { broken_class.all.includes(:commenters).to_a }
+  end
+end
+
+# Wraps Store#all/#find to count reads, mirroring test_orm_eager_loading.rb's
+# CountingStore so this file has no load-order dependency on it.
+class CountingThroughStore < 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