1 files changed, 84 insertions, 0 deletions
diff --git a/activerecord/test/cases/null_relation_test.rb b/activerecord/test/cases/null_relation_test.rb
new file mode 100644
index 0000000000..17527568f8
--- /dev/null
+++ b/activerecord/test/cases/null_relation_test.rb
@@ -0,0 +1,84 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/developer"
+require "models/comment"
+require "models/post"
+require "models/topic"
+
+class NullRelationTest < ActiveRecord::TestCase
+  fixtures :posts, :comments
+
+  def test_none
+    assert_no_queries(ignore_none: false) do
+      assert_equal [], Developer.none
+      assert_equal [], Developer.all.none
+    end
+  end
+
+  def test_none_chainable
+    assert_no_queries(ignore_none: false) do
+      assert_equal [], Developer.none.where(name: "David")
+    end
+  end
+
+  def test_none_chainable_to_existing_scope_extension_method
+    assert_no_queries(ignore_none: false) do
+      assert_equal 1, Topic.anonymous_extension.none.one
+    end
+  end
+
+  def test_none_chained_to_methods_firing_queries_straight_to_db
+    assert_no_queries(ignore_none: false) do
+      assert_equal [],    Developer.none.pluck(:id, :name)
+      assert_equal 0,     Developer.none.delete_all
+      assert_equal 0,     Developer.none.update_all(name: "David")
+      assert_equal 0,     Developer.none.delete(1)
+      assert_equal false, Developer.none.exists?(1)
+    end
+  end
+
+  def test_null_relation_content_size_methods
+    assert_no_queries(ignore_none: false) do
+      assert_equal 0,     Developer.none.size
+      assert_equal 0,     Developer.none.count
+      assert_equal true,  Developer.none.empty?
+      assert_equal true,  Developer.none.none?
+      assert_equal false, Developer.none.any?
+      assert_equal false, Developer.none.one?
+      assert_equal false, Developer.none.many?
+    end
+  end
+
+  def test_null_relation_metadata_methods
+    assert_equal "", Developer.none.to_sql
+    assert_equal({}, Developer.none.where_values_hash)
+  end
+
+  def test_null_relation_where_values_hash
+    assert_equal({ "salary" => 100_000 }, Developer.none.where(salary: 100_000).where_values_hash)
+  end
+
+  [:count, :sum].each do |method|
+    define_method "test_null_relation_#{method}" do
+      assert_no_queries(ignore_none: false) do
+        assert_equal 0, Comment.none.public_send(method, :id)
+        assert_equal Hash.new, Comment.none.group(:post_id).public_send(method, :id)
+      end
+    end
+  end
+
+  [:average, :minimum, :maximum].each do |method|
+    define_method "test_null_relation_#{method}" do
+      assert_no_queries(ignore_none: false) do
+        assert_nil Comment.none.public_send(method, :id)
+        assert_equal Hash.new, Comment.none.group(:post_id).public_send(method, :id)
+      end
+    end
+  end
+
+  def test_null_relation_in_where_condition
+    assert_operator Comment.count, :>, 0 # precondition, make sure there are comments.
+    assert_equal 0, Comment.where(post_id: Post.none).count
+  end
+end