Extract `NullRelationTest` from `RelationTest`

`test/cases/relations_test.rb` file has too much lines (2000 over).
So I extracted `NullRelationTest` to the dedicated file.

2 files changed, 128 insertions, 118 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..0bb9097495
--- /dev/null
+++ b/activerecord/test/cases/null_relation_test.rb
@@ -0,0 +1,128 @@
+require "cases/helper"
+require "models/aircraft"
+require "models/engine"
+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_calculations_methods
+    assert_no_queries(ignore_none: false) do
+      assert_equal 0, Developer.none.count
+      assert_equal 0, Developer.none.calculate(:count, nil)
+      assert_nil Developer.none.calculate(:average, "salary")
+    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
+
+  def test_null_relation_sum
+    ac = Aircraft.new
+    assert_equal Hash.new, ac.engines.group(:id).sum(:id)
+    assert_equal 0, ac.engines.count
+    ac.save
+    assert_equal Hash.new, ac.engines.group(:id).sum(:id)
+    assert_equal 0, ac.engines.count
+  end
+
+  def test_null_relation_count
+    ac = Aircraft.new
+    assert_equal Hash.new, ac.engines.group(:id).count
+    assert_equal 0, ac.engines.count
+    ac.save
+    assert_equal Hash.new, ac.engines.group(:id).count
+    assert_equal 0, ac.engines.count
+  end
+
+  def test_null_relation_size
+    ac = Aircraft.new
+    assert_equal Hash.new, ac.engines.group(:id).size
+    assert_equal 0, ac.engines.size
+    ac.save
+    assert_equal Hash.new, ac.engines.group(:id).size
+    assert_equal 0, ac.engines.size
+  end
+
+  def test_null_relation_average
+    ac = Aircraft.new
+    assert_equal Hash.new, ac.engines.group(:car_id).average(:id)
+    assert_nil ac.engines.average(:id)
+    ac.save
+    assert_equal Hash.new, ac.engines.group(:car_id).average(:id)
+    assert_nil ac.engines.average(:id)
+  end
+
+  def test_null_relation_minimum
+    ac = Aircraft.new
+    assert_equal Hash.new, ac.engines.group(:car_id).minimum(:id)
+    assert_nil ac.engines.minimum(:id)
+    ac.save
+    assert_equal Hash.new, ac.engines.group(:car_id).minimum(:id)
+    assert_nil ac.engines.minimum(:id)
+  end
+
+  def test_null_relation_maximum
+    ac = Aircraft.new
+    assert_equal Hash.new, ac.engines.group(:car_id).maximum(:id)
+    assert_nil ac.engines.maximum(:id)
+    ac.save
+    assert_equal Hash.new, ac.engines.group(:car_id).maximum(:id)
+    assert_nil ac.engines.maximum(:id)
+  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
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index eb3449b331..b91ba8341c 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -15,7 +15,6 @@ require "models/car"
 require "models/engine"
 require "models/tyre"
 require "models/minivan"
-require "models/aircraft"
 require "models/possession"
 require "models/reader"
 require "models/categorization"
@@ -420,123 +419,6 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal [2, 4, 6, 8, 10], even_ids.sort
   end
 
-  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_calculations_methods
-    assert_no_queries(ignore_none: false) do
-      assert_equal 0, Developer.none.count
-      assert_equal 0, Developer.none.calculate(:count, nil)
-      assert_nil Developer.none.calculate(:average, "salary")
-    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
-
-  def test_null_relation_sum
-    ac = Aircraft.new
-    assert_equal Hash.new, ac.engines.group(:id).sum(:id)
-    assert_equal 0, ac.engines.count
-    ac.save
-    assert_equal Hash.new, ac.engines.group(:id).sum(:id)
-    assert_equal 0, ac.engines.count
-  end
-
-  def test_null_relation_count
-    ac = Aircraft.new
-    assert_equal Hash.new, ac.engines.group(:id).count
-    assert_equal 0, ac.engines.count
-    ac.save
-    assert_equal Hash.new, ac.engines.group(:id).count
-    assert_equal 0, ac.engines.count
-  end
-
-  def test_null_relation_size
-    ac = Aircraft.new
-    assert_equal Hash.new, ac.engines.group(:id).size
-    assert_equal 0, ac.engines.size
-    ac.save
-    assert_equal Hash.new, ac.engines.group(:id).size
-    assert_equal 0, ac.engines.size
-  end
-
-  def test_null_relation_average
-    ac = Aircraft.new
-    assert_equal Hash.new, ac.engines.group(:car_id).average(:id)
-    assert_nil ac.engines.average(:id)
-    ac.save
-    assert_equal Hash.new, ac.engines.group(:car_id).average(:id)
-    assert_nil ac.engines.average(:id)
-  end
-
-  def test_null_relation_minimum
-    ac = Aircraft.new
-    assert_equal Hash.new, ac.engines.group(:car_id).minimum(:id)
-    assert_nil ac.engines.minimum(:id)
-    ac.save
-    assert_equal Hash.new, ac.engines.group(:car_id).minimum(:id)
-    assert_nil ac.engines.minimum(:id)
-  end
-
-  def test_null_relation_maximum
-    ac = Aircraft.new
-    assert_equal Hash.new, ac.engines.group(:car_id).maximum(:id)
-    assert_nil ac.engines.maximum(:id)
-    ac.save
-    assert_equal Hash.new, ac.engines.group(:car_id).maximum(:id)
-    assert_nil ac.engines.maximum(:id)
-  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).to_a.size
-  end
-
   def test_joins_with_nil_argument
     assert_nothing_raised { DependentFirm.joins(nil).first }
   end