test: cover OrmNPlusOneDetectorTest and teardown

test/test_orm_n_plus_one_detector.rb

@@ -0,0 +1,161 @@
+require 'minitest/autorun'
+require 'prism'
+require 'tmpdir'
+require 'stringio'
+
+class OrmNPlusOneDetectorTest < Minitest::Test
+  def setup
+    @dir = Dir.mktmpdir('prism-n-plus-one-store')
+    @store = Prism::Orm::Store.new(File.join(@dir, 'test.pstore'))
+    @store.create_table(:authors, %w[id name])
+    @store.create_table(:posts, %w[id title author_id])
+    @store.create_table(:bios, %w[id author_id headline])
+
+    author_class = Class.new(Prism::Orm::Model) do
+      table_name :authors
+      has_many :posts, class_name: 'Post', foreign_key: 'author_id'
+      has_one :bio, class_name: 'Bio', foreign_key: 'author_id'
+    end
+    post_class = Class.new(Prism::Orm::Model) do
+      table_name :posts
+      belongs_to :author, class_name: 'Author', foreign_key: 'author_id'
+    end
+    bio_class = Class.new(Prism::Orm::Model) do
+      table_name :bios
+      belongs_to :author, class_name: 'Author', foreign_key: 'author_id'
+    end
+    [author_class, post_class, bio_class].each { |klass| klass.store = @store }
+    Object.const_set(:Author, author_class)
+    Object.const_set(:Post, post_class)
+    Object.const_set(:Bio, bio_class)
+
+    @io = StringIO.new
+  end
+
+  def teardown
+    Prism::Orm::NPlusOneDetector.disable!
+    Prism::Orm::NPlusOneDetector.reset!
+    FileUtils.remove_entry(@dir)
+    %i[Author Post Bio].each { |name| Object.send(:remove_const, name) if Object.const_defined?(name) }
+  end
+
+  def create_authors_with_posts(count)
+    count.times do |i|
+      author = Author.create!(name: "author#{i}")
+      Post.create!(title: "post#{i}", author_id: author.id)
+      author
+    end
+  end
+
+  def test_disabled_by_default_never_warns_even_on_an_obvious_n_plus_one
+    create_authors_with_posts(5)
+    Author.all.to_a.each { |author| author.posts.to_a }
+    Prism::Orm::NPlusOneDetector.report!
+    assert_empty @io.string
+  end
+
+  def test_below_threshold_does_not_warn
+    Prism::Orm::NPlusOneDetector.enable!(threshold: 2, io: @io)
+    create_authors_with_posts(1)
+
+    Author.all.to_a.each { |author| author.posts.to_a }
+    Prism::Orm::NPlusOneDetector.report!
+
+    assert_empty @io.string
+  end
+
+  def test_reaching_threshold_across_distinct_owners_warns
+    Prism::Orm::NPlusOneDetector.enable!(threshold: 2, io: @io)
+    create_authors_with_posts(3)
+
+    Author.all.to_a.each { |author| author.posts.to_a }
+    Prism::Orm::NPlusOneDetector.report!
+
+    assert_match(/N\+1 query detected: Author#posts lazily loaded for 3 separate Author records/, @io.string)
+    assert_match(/\.includes\(:posts\)/, @io.string)
+  end
+
+  def test_preloaded_via_includes_never_counts_as_a_lazy_load
+    Prism::Orm::NPlusOneDetector.enable!(threshold: 2, io: @io)
+    create_authors_with_posts(3)
+
+    Author.all.includes(:posts).to_a.each { |author| author.posts.to_a }
+    Prism::Orm::NPlusOneDetector.report!
+
+    assert_empty @io.string
+  end
+
+  def test_repeated_reads_on_the_same_owner_do_not_inflate_the_count
+    Prism::Orm::NPlusOneDetector.enable!(threshold: 2, io: @io)
+    create_authors_with_posts(1)
+    author = Author.first
+
+    5.times { author.posts.to_a }
+    Prism::Orm::NPlusOneDetector.report!
+
+    assert_empty @io.string, 'one owner read five times is still one owner, not five'
+  end
+
+  def test_two_different_associations_are_tracked_and_reported_independently
+    Prism::Orm::NPlusOneDetector.enable!(threshold: 2, io: @io)
+    3.times do |i|
+      author = Author.create!(name: "author#{i}")
+      Post.create!(title: "post#{i}", author_id: author.id)
+      Bio.create!(headline: "bio#{i}", author_id: author.id)
+    end
+
+    Author.all.to_a.each do |author|
+      author.posts.to_a
+      author.bio
+    end
+    Prism::Orm::NPlusOneDetector.report!
+
+    assert_match(/Author#posts lazily loaded for 3/, @io.string)
+    assert_match(/Author#bio lazily loaded for 3/, @io.string)
+  end
+
+  def test_belongs_to_lazy_loads_across_distinct_children_are_detected_too
+    Prism::Orm::NPlusOneDetector.enable!(threshold: 2, io: @io)
+    author = Author.create!(name: 'shared')
+    3.times { |i| Post.create!(title: "post#{i}", author_id: author.id) }
+
+    Post.all.to_a.each(&:author)
+    Prism::Orm::NPlusOneDetector.report!
+
+    assert_match(/Post#author lazily loaded for 3 separate Post records/, @io.string)
+  end
+
+  def test_raise_on_violation_raises_instead_of_only_logging
+    Prism::Orm::NPlusOneDetector.enable!(threshold: 2, io: @io, raise_on_violation: true)
+    create_authors_with_posts(2)
+
+    error = assert_raises(Prism::Orm::NPlusOneViolation) do
+      Author.all.to_a.each { |author| author.posts.to_a }
+      Prism::Orm::NPlusOneDetector.report!
+    end
+    assert_match(/Author#posts/, error.message)
+  end
+
+  def test_reset_clears_the_tracker_between_requests
+    Prism::Orm::NPlusOneDetector.enable!(threshold: 2, io: @io)
+    create_authors_with_posts(1)
+    author = Author.first
+
+    author.posts.to_a
+    Prism::Orm::NPlusOneDetector.reset!
+    author.posts.to_a
+    Prism::Orm::NPlusOneDetector.report!
+
+    assert_empty @io.string, 'reset! between requests must not let counts carry over'
+  end
+
+  def test_context_is_included_in_the_warning_line
+    Prism::Orm::NPlusOneDetector.enable!(threshold: 2, io: @io)
+    create_authors_with_posts(2)
+
+    Author.all.to_a.each { |author| author.posts.to_a }
+    Prism::Orm::NPlusOneDetector.report!(method: 'GET', path: '/authors')
+
+    assert_match(%r{method=\"GET\" path=\"/authors\"}, @io.string)
+  end
+end