Merge Arel into Active Record

32 files changed, 1361 insertions, 0 deletions

diff --git a/activerecord/test/cases/arel/nodes/and_test.rb b/activerecord/test/cases/arel/nodes/and_test.rb
new file mode 100644
index 0000000000..de63e0bb31
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/and_test.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'And' do
+      describe 'equality' do
+        it 'is equal with equal ivars' do
+          array = [And.new(['foo', 'bar']), And.new(['foo', 'bar'])]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with different ivars' do
+          array = [And.new(['foo', 'bar']), And.new(['foo', 'baz'])]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
+
diff --git a/activerecord/test/cases/arel/nodes/as_test.rb b/activerecord/test/cases/arel/nodes/as_test.rb
new file mode 100644
index 0000000000..09c8aa8d62
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/as_test.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'As' do
+      describe '#as' do
+        it 'makes an AS node' do
+          attr = Table.new(:users)[:id]
+          as = attr.as(Arel.sql('foo'))
+          assert_equal attr, as.left
+          assert_equal 'foo', as.right
+        end
+
+        it 'converts right to SqlLiteral if a string' do
+          attr = Table.new(:users)[:id]
+          as = attr.as('foo')
+          assert_kind_of Arel::Nodes::SqlLiteral, as.right
+        end
+      end
+
+      describe 'equality' do
+        it 'is equal with equal ivars' do
+          array = [As.new('foo', 'bar'), As.new('foo', 'bar')]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with different ivars' do
+          array = [As.new('foo', 'bar'), As.new('foo', 'baz')]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/ascending_test.rb b/activerecord/test/cases/arel/nodes/ascending_test.rb
new file mode 100644
index 0000000000..5c73e69fa5
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/ascending_test.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    class TestAscending < Arel::Test
+      def test_construct
+        ascending = Ascending.new 'zomg'
+        assert_equal 'zomg', ascending.expr
+      end
+
+      def test_reverse
+        ascending = Ascending.new 'zomg'
+        descending = ascending.reverse
+        assert_kind_of Descending, descending
+        assert_equal ascending.expr, descending.expr
+      end
+
+      def test_direction
+        ascending = Ascending.new 'zomg'
+        assert_equal :asc, ascending.direction
+      end
+
+      def test_ascending?
+        ascending = Ascending.new 'zomg'
+        assert ascending.ascending?
+      end
+
+      def test_descending?
+        ascending = Ascending.new 'zomg'
+        assert !ascending.descending?
+      end
+
+      def test_equality_with_same_ivars
+        array = [Ascending.new('zomg'), Ascending.new('zomg')]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [Ascending.new('zomg'), Ascending.new('zomg!')]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/bin_test.rb b/activerecord/test/cases/arel/nodes/bin_test.rb
new file mode 100644
index 0000000000..923a296adf
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/bin_test.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    class TestBin < Arel::Test
+      def test_new
+        assert Arel::Nodes::Bin.new('zomg')
+      end
+
+      def test_default_to_sql
+        viz  = Arel::Visitors::ToSql.new Table.engine.connection_pool
+        node = Arel::Nodes::Bin.new(Arel.sql('zomg'))
+        assert_equal 'zomg', viz.accept(node, Collectors::SQLString.new).value
+      end
+
+      def test_mysql_to_sql
+        viz  = Arel::Visitors::MySQL.new Table.engine.connection_pool
+        node = Arel::Nodes::Bin.new(Arel.sql('zomg'))
+        assert_equal 'BINARY zomg', viz.accept(node, Collectors::SQLString.new).value
+      end
+
+      def test_equality_with_same_ivars
+        array = [Bin.new('zomg'), Bin.new('zomg')]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [Bin.new('zomg'), Bin.new('zomg!')]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/binary_test.rb b/activerecord/test/cases/arel/nodes/binary_test.rb
new file mode 100644
index 0000000000..0bea35f7dd
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/binary_test.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'Binary' do
+      describe '#hash' do
+        it 'generates a hash based on its value' do
+          eq = Equality.new('foo', 'bar')
+          eq2 = Equality.new('foo', 'bar')
+          eq3 = Equality.new('bar', 'baz')
+
+          assert_equal eq.hash, eq2.hash
+          refute_equal eq.hash, eq3.hash
+        end
+
+        it 'generates a hash specific to its class' do
+          eq = Equality.new('foo', 'bar')
+          neq = NotEqual.new('foo', 'bar')
+
+          refute_equal eq.hash, neq.hash
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/bind_param_test.rb b/activerecord/test/cases/arel/nodes/bind_param_test.rb
new file mode 100644
index 0000000000..665581edce
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/bind_param_test.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'BindParam' do
+      it 'is equal to other bind params with the same value' do
+        BindParam.new(1).must_equal(BindParam.new(1))
+        BindParam.new("foo").must_equal(BindParam.new("foo"))
+      end
+
+      it 'is not equal to other nodes' do
+        BindParam.new(nil).wont_equal(Node.new)
+      end
+
+      it 'is not equal to bind params with different values' do
+        BindParam.new(1).wont_equal(BindParam.new(2))
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/case_test.rb b/activerecord/test/cases/arel/nodes/case_test.rb
new file mode 100644
index 0000000000..70364fe6ab
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/case_test.rb
@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'Case' do
+      describe '#initialize' do
+        it 'sets case expression from first argument' do
+          node = Case.new 'foo'
+
+          assert_equal 'foo', node.case
+        end
+
+        it 'sets default case from second argument' do
+          node = Case.new nil, 'bar'
+
+          assert_equal 'bar', node.default
+        end
+      end
+
+      describe '#clone' do
+        it 'clones case, conditions and default' do
+          foo = Nodes.build_quoted 'foo'
+
+          node = Case.new
+          node.case = foo
+          node.conditions = [When.new(foo, foo)]
+          node.default = foo
+
+          dolly = node.clone
+
+          assert_equal dolly.case, node.case
+          refute_same  dolly.case, node.case
+
+          assert_equal dolly.conditions, node.conditions
+          refute_same  dolly.conditions, node.conditions
+
+          assert_equal dolly.default, node.default
+          refute_same  dolly.default, node.default
+        end
+      end
+
+      describe 'equality' do
+        it 'is equal with equal ivars' do
+          foo = Nodes.build_quoted 'foo'
+          one = Nodes.build_quoted 1
+          zero = Nodes.build_quoted 0
+
+          case1 = Case.new foo
+          case1.conditions = [When.new(foo, one)]
+          case1.default = Else.new zero
+
+          case2 = Case.new foo
+          case2.conditions = [When.new(foo, one)]
+          case2.default = Else.new zero
+
+          array = [case1, case2]
+
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with different ivars' do
+          foo = Nodes.build_quoted 'foo'
+          bar = Nodes.build_quoted 'bar'
+          one = Nodes.build_quoted 1
+          zero = Nodes.build_quoted 0
+
+          case1 = Case.new foo
+          case1.conditions = [When.new(foo, one)]
+          case1.default = Else.new zero
+
+          case2 = Case.new foo
+          case2.conditions = [When.new(bar, one)]
+          case2.default = Else.new zero
+
+          array = [case1, case2]
+
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/casted_test.rb b/activerecord/test/cases/arel/nodes/casted_test.rb
new file mode 100644
index 0000000000..a6e2dd2294
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/casted_test.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe Casted do
+      describe '#hash' do
+        it 'is equal when eql? returns true' do
+          one = Casted.new 1, 2
+          also_one = Casted.new 1, 2
+
+          assert_equal one.hash, also_one.hash
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/count_test.rb b/activerecord/test/cases/arel/nodes/count_test.rb
new file mode 100644
index 0000000000..28d8481993
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/count_test.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+class Arel::Nodes::CountTest < Arel::Spec
+  describe "as" do
+    it 'should alias the count' do
+      table = Arel::Table.new :users
+      table[:id].count.as('foo').to_sql.must_be_like %{
+        COUNT("users"."id") AS foo
+      }
+    end
+  end
+
+  describe "eq" do
+    it "should compare the count" do
+      table = Arel::Table.new :users
+      table[:id].count.eq(2).to_sql.must_be_like %{
+        COUNT("users"."id") = 2
+      }
+    end
+  end
+
+  describe 'equality' do
+    it 'is equal with equal ivars' do
+      array = [Arel::Nodes::Count.new('foo'), Arel::Nodes::Count.new('foo')]
+      assert_equal 1, array.uniq.size
+    end
+
+    it 'is not equal with different ivars' do
+      array = [Arel::Nodes::Count.new('foo'), Arel::Nodes::Count.new('foo!')]
+      assert_equal 2, array.uniq.size
+    end
+  end
+
+  describe 'math' do
+    it 'allows mathematical functions' do
+      table = Arel::Table.new :users
+      (table[:id].count + 1).to_sql.must_be_like %{
+        (COUNT("users"."id") + 1)
+      }
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/delete_statement_test.rb b/activerecord/test/cases/arel/nodes/delete_statement_test.rb
new file mode 100644
index 0000000000..ada8964646
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/delete_statement_test.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+describe Arel::Nodes::DeleteStatement do
+  describe "#clone" do
+    it "clones wheres" do
+      statement = Arel::Nodes::DeleteStatement.new
+      statement.wheres = %w[a b c]
+
+      dolly = statement.clone
+      dolly.wheres.must_equal statement.wheres
+      dolly.wheres.wont_be_same_as statement.wheres
+    end
+  end
+
+  describe 'equality' do
+    it 'is equal with equal ivars' do
+      statement1 = Arel::Nodes::DeleteStatement.new
+      statement1.wheres = %w[a b c]
+      statement2 = Arel::Nodes::DeleteStatement.new
+      statement2.wheres = %w[a b c]
+      array = [statement1, statement2]
+      assert_equal 1, array.uniq.size
+    end
+
+    it 'is not equal with different ivars' do
+      statement1 = Arel::Nodes::DeleteStatement.new
+      statement1.wheres = %w[a b c]
+      statement2 = Arel::Nodes::DeleteStatement.new
+      statement2.wheres = %w[1 2 3]
+      array = [statement1, statement2]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/descending_test.rb b/activerecord/test/cases/arel/nodes/descending_test.rb
new file mode 100644
index 0000000000..5fe0ba62b0
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/descending_test.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    class TestDescending < Arel::Test
+      def test_construct
+        descending = Descending.new 'zomg'
+        assert_equal 'zomg', descending.expr
+      end
+
+      def test_reverse
+        descending = Descending.new 'zomg'
+        ascending = descending.reverse
+        assert_kind_of Ascending, ascending
+        assert_equal descending.expr, ascending.expr
+      end
+
+      def test_direction
+        descending = Descending.new 'zomg'
+        assert_equal :desc, descending.direction
+      end
+
+      def test_ascending?
+        descending = Descending.new 'zomg'
+        assert !descending.ascending?
+      end
+
+      def test_descending?
+        descending = Descending.new 'zomg'
+        assert descending.descending?
+      end
+
+      def test_equality_with_same_ivars
+        array = [Descending.new('zomg'), Descending.new('zomg')]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [Descending.new('zomg'), Descending.new('zomg!')]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/distinct_test.rb b/activerecord/test/cases/arel/nodes/distinct_test.rb
new file mode 100644
index 0000000000..465700118e
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/distinct_test.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'Distinct' do
+      describe 'equality' do
+        it 'is equal to other distinct nodes' do
+          array = [Distinct.new, Distinct.new]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with other nodes' do
+          array = [Distinct.new, Node.new]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
+
diff --git a/activerecord/test/cases/arel/nodes/equality_test.rb b/activerecord/test/cases/arel/nodes/equality_test.rb
new file mode 100644
index 0000000000..28a74de321
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/equality_test.rb
@@ -0,0 +1,85 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'equality' do
+      # FIXME: backwards compat
+      describe 'backwards compat' do
+        describe 'operator' do
+          it 'returns :==' do
+            attr = Table.new(:users)[:id]
+            left  = attr.eq(10)
+            left.operator.must_equal :==
+          end
+        end
+
+        describe 'operand1' do
+          it "should equal left" do
+            attr = Table.new(:users)[:id]
+            left  = attr.eq(10)
+            left.left.must_equal left.operand1
+          end
+        end
+
+        describe 'operand2' do
+          it "should equal right" do
+            attr = Table.new(:users)[:id]
+            left  = attr.eq(10)
+            left.right.must_equal left.operand2
+          end
+        end
+
+        describe 'to_sql' do
+          it 'takes an engine' do
+            engine = FakeRecord::Base.new
+            engine.connection.extend Module.new {
+              attr_accessor :quote_count
+              def quote(*args) @quote_count += 1; super; end
+              def quote_column_name(*args) @quote_count += 1; super; end
+              def quote_table_name(*args) @quote_count += 1; super; end
+            }
+            engine.connection.quote_count = 0
+
+            attr = Table.new(:users)[:id]
+            test = attr.eq(10)
+            test.to_sql engine
+            engine.connection.quote_count.must_equal 3
+          end
+        end
+      end
+
+      describe 'or' do
+        it 'makes an OR node' do
+          attr = Table.new(:users)[:id]
+          left  = attr.eq(10)
+          right = attr.eq(11)
+          node  = left.or right
+          node.expr.left.must_equal left
+          node.expr.right.must_equal right
+        end
+      end
+
+      describe 'and' do
+        it 'makes and AND node' do
+          attr = Table.new(:users)[:id]
+          left  = attr.eq(10)
+          right = attr.eq(11)
+          node  = left.and right
+          node.left.must_equal left
+          node.right.must_equal right
+        end
+      end
+
+      it 'is equal with equal ivars' do
+        array = [Equality.new('foo', 'bar'), Equality.new('foo', 'bar')]
+        assert_equal 1, array.uniq.size
+      end
+
+      it 'is not equal with different ivars' do
+        array = [Equality.new('foo', 'bar'), Equality.new('foo', 'baz')]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/extract_test.rb b/activerecord/test/cases/arel/nodes/extract_test.rb
new file mode 100644
index 0000000000..f6dc1626a4
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/extract_test.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+class Arel::Nodes::ExtractTest < Arel::Spec
+  it "should extract field" do
+    table = Arel::Table.new :users
+    table[:timestamp].extract('date').to_sql.must_be_like %{
+      EXTRACT(DATE FROM "users"."timestamp")
+    }
+  end
+
+  describe "as" do
+    it 'should alias the extract' do
+      table = Arel::Table.new :users
+      table[:timestamp].extract('date').as('foo').to_sql.must_be_like %{
+        EXTRACT(DATE FROM "users"."timestamp") AS foo
+      }
+    end
+
+    it 'should not mutate the extract' do
+      table = Arel::Table.new :users
+      extract = table[:timestamp].extract('date')
+      before = extract.dup
+      extract.as('foo')
+      assert_equal extract, before
+    end
+  end
+
+  describe 'equality' do
+    it 'is equal with equal ivars' do
+      table = Arel::Table.new :users
+      array = [table[:attr].extract('foo'), table[:attr].extract('foo')]
+      assert_equal 1, array.uniq.size
+    end
+
+    it 'is not equal with different ivars' do
+      table = Arel::Table.new :users
+      array = [table[:attr].extract('foo'), table[:attr].extract('bar')]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/false_test.rb b/activerecord/test/cases/arel/nodes/false_test.rb
new file mode 100644
index 0000000000..8b91dc227c
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/false_test.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'False' do
+      describe 'equality' do
+        it 'is equal to other false nodes' do
+          array = [False.new, False.new]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with other nodes' do
+          array = [False.new, Node.new]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
+
diff --git a/activerecord/test/cases/arel/nodes/grouping_test.rb b/activerecord/test/cases/arel/nodes/grouping_test.rb
new file mode 100644
index 0000000000..7ad1584f0f
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/grouping_test.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    class GroupingTest < Arel::Spec
+      it 'should create Equality nodes' do
+        grouping = Grouping.new(Nodes.build_quoted('foo'))
+        grouping.eq('foo').to_sql.must_be_like %q{('foo') = 'foo'}
+      end
+
+      describe 'equality' do
+        it 'is equal with equal ivars' do
+          array = [Grouping.new('foo'), Grouping.new('foo')]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with different ivars' do
+          array = [Grouping.new('foo'), Grouping.new('bar')]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
+
diff --git a/activerecord/test/cases/arel/nodes/infix_operation_test.rb b/activerecord/test/cases/arel/nodes/infix_operation_test.rb
new file mode 100644
index 0000000000..28a4710dc0
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/infix_operation_test.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    class TestInfixOperation < Arel::Test
+      def test_construct
+        operation = InfixOperation.new :+, 1, 2
+        assert_equal :+, operation.operator
+        assert_equal 1, operation.left
+        assert_equal 2, operation.right
+      end
+
+      def test_operation_alias
+        operation = InfixOperation.new :+, 1, 2
+        aliaz = operation.as('zomg')
+        assert_kind_of As, aliaz
+        assert_equal operation, aliaz.left
+        assert_equal 'zomg', aliaz.right
+      end
+
+      def test_operation_ordering
+        operation = InfixOperation.new :+, 1, 2
+        ordering = operation.desc
+        assert_kind_of Descending, ordering
+        assert_equal operation, ordering.expr
+        assert ordering.descending?
+      end
+
+      def test_equality_with_same_ivars
+        array = [InfixOperation.new(:+, 1, 2), InfixOperation.new(:+, 1, 2)]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [InfixOperation.new(:+, 1, 2), InfixOperation.new(:+, 1, 3)]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/insert_statement_test.rb b/activerecord/test/cases/arel/nodes/insert_statement_test.rb
new file mode 100644
index 0000000000..87f9d83a32
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/insert_statement_test.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+describe Arel::Nodes::InsertStatement do
+  describe "#clone" do
+    it "clones columns and values" do
+      statement = Arel::Nodes::InsertStatement.new
+      statement.columns = %w[a b c]
+      statement.values  = %w[x y z]
+
+      dolly = statement.clone
+      dolly.columns.must_equal statement.columns
+      dolly.values.must_equal statement.values
+
+      dolly.columns.wont_be_same_as statement.columns
+      dolly.values.wont_be_same_as statement.values
+    end
+  end
+
+  describe 'equality' do
+    it 'is equal with equal ivars' do
+      statement1 = Arel::Nodes::InsertStatement.new
+      statement1.columns = %w[a b c]
+      statement1.values  = %w[x y z]
+      statement2 = Arel::Nodes::InsertStatement.new
+      statement2.columns = %w[a b c]
+      statement2.values  = %w[x y z]
+      array = [statement1, statement2]
+      assert_equal 1, array.uniq.size
+    end
+
+    it 'is not equal with different ivars' do
+      statement1 = Arel::Nodes::InsertStatement.new
+      statement1.columns = %w[a b c]
+      statement1.values  = %w[x y z]
+      statement2 = Arel::Nodes::InsertStatement.new
+      statement2.columns = %w[a b c]
+      statement2.values  = %w[1 2 3]
+      array = [statement1, statement2]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/named_function_test.rb b/activerecord/test/cases/arel/nodes/named_function_test.rb
new file mode 100644
index 0000000000..30f6dac595
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/named_function_test.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    class TestNamedFunction < Arel::Test
+      def test_construct
+        function = NamedFunction.new 'omg', 'zomg'
+        assert_equal 'omg', function.name
+        assert_equal 'zomg', function.expressions
+      end
+
+      def test_function_alias
+        function = NamedFunction.new 'omg', 'zomg'
+        function = function.as('wth')
+        assert_equal 'omg', function.name
+        assert_equal 'zomg', function.expressions
+        assert_kind_of SqlLiteral, function.alias
+        assert_equal 'wth', function.alias
+      end
+
+      def test_construct_with_alias
+        function = NamedFunction.new 'omg', 'zomg', 'wth'
+        assert_equal 'omg', function.name
+        assert_equal 'zomg', function.expressions
+        assert_kind_of SqlLiteral, function.alias
+        assert_equal 'wth', function.alias
+      end
+
+      def test_equality_with_same_ivars
+        array = [
+          NamedFunction.new('omg', 'zomg', 'wth'),
+          NamedFunction.new('omg', 'zomg', 'wth')
+        ]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [
+          NamedFunction.new('omg', 'zomg', 'wth'),
+          NamedFunction.new('zomg', 'zomg', 'wth')
+        ]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/node_test.rb b/activerecord/test/cases/arel/nodes/node_test.rb
new file mode 100644
index 0000000000..c1d3a01d1c
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/node_test.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  class TestNode < Arel::Test
+    def test_includes_factory_methods
+      assert Node.new.respond_to?(:create_join)
+    end
+
+    def test_all_nodes_are_nodes
+      Nodes.constants.map { |k|
+        Nodes.const_get(k)
+      }.grep(Class).each do |klass|
+        next if Nodes::SqlLiteral == klass
+        next if Nodes::BindParam == klass
+        next if klass.name =~ /^Arel::Nodes::(?:Test|.*Test$)/
+        assert klass.ancestors.include?(Nodes::Node), klass.name
+      end
+    end
+
+    def test_each
+      list = []
+      node = Nodes::Node.new
+      node.each { |n| list << n }
+      assert_equal [node], list
+    end
+
+    def test_generator
+      list = []
+      node = Nodes::Node.new
+      node.each.each { |n| list << n }
+      assert_equal [node], list
+    end
+
+    def test_enumerable
+      node = Nodes::Node.new
+      assert_kind_of Enumerable, node
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/not_test.rb b/activerecord/test/cases/arel/nodes/not_test.rb
new file mode 100644
index 0000000000..15f94a6f10
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/not_test.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'not' do
+      describe '#not' do
+        it 'makes a NOT node' do
+          attr = Table.new(:users)[:id]
+          expr  = attr.eq(10)
+          node  = expr.not
+          node.must_be_kind_of Not
+          node.expr.must_equal expr
+        end
+      end
+
+      describe 'equality' do
+        it 'is equal with equal ivars' do
+          array = [Not.new('foo'), Not.new('foo')]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with different ivars' do
+          array = [Not.new('foo'), Not.new('baz')]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/or_test.rb b/activerecord/test/cases/arel/nodes/or_test.rb
new file mode 100644
index 0000000000..4f8d56d165
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/or_test.rb
@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'or' do
+      describe '#or' do
+        it 'makes an OR node' do
+          attr = Table.new(:users)[:id]
+          left  = attr.eq(10)
+          right = attr.eq(11)
+          node  = left.or right
+          node.expr.left.must_equal left
+          node.expr.right.must_equal right
+
+          oror = node.or(right)
+          oror.expr.left.must_equal node
+          oror.expr.right.must_equal right
+        end
+      end
+
+      describe 'equality' do
+        it 'is equal with equal ivars' do
+          array = [Or.new('foo', 'bar'), Or.new('foo', 'bar')]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with different ivars' do
+          array = [Or.new('foo', 'bar'), Or.new('foo', 'baz')]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/over_test.rb b/activerecord/test/cases/arel/nodes/over_test.rb
new file mode 100644
index 0000000000..c9804c395f
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/over_test.rb
@@ -0,0 +1,68 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+class Arel::Nodes::OverTest < Arel::Spec
+  describe 'as' do
+    it 'should alias the expression' do
+      table = Arel::Table.new :users
+      table[:id].count.over.as('foo').to_sql.must_be_like %{
+        COUNT("users"."id") OVER () AS foo
+      }
+    end
+  end
+
+  describe 'with literal' do
+    it 'should reference the window definition by name' do
+      table = Arel::Table.new :users
+      table[:id].count.over('foo').to_sql.must_be_like %{
+        COUNT("users"."id") OVER "foo"
+      }
+    end
+  end
+
+  describe 'with SQL literal' do
+    it 'should reference the window definition by name' do
+      table = Arel::Table.new :users
+      table[:id].count.over(Arel.sql('foo')).to_sql.must_be_like %{
+        COUNT("users"."id") OVER foo
+      }
+    end
+  end
+
+  describe 'with no expression' do
+    it 'should use empty definition' do
+      table = Arel::Table.new :users
+      table[:id].count.over.to_sql.must_be_like %{
+        COUNT("users"."id") OVER ()
+      }
+    end
+  end
+
+  describe 'with expression' do
+    it 'should use definition in sub-expression' do
+      table = Arel::Table.new :users
+      window = Arel::Nodes::Window.new.order(table['foo'])
+      table[:id].count.over(window).to_sql.must_be_like %{
+        COUNT("users"."id") OVER (ORDER BY \"users\".\"foo\")
+      }
+    end
+  end
+
+  describe 'equality' do
+    it 'is equal with equal ivars' do
+      array = [
+        Arel::Nodes::Over.new('foo', 'bar'),
+        Arel::Nodes::Over.new('foo', 'bar')
+      ]
+      assert_equal 1, array.uniq.size
+    end
+
+    it 'is not equal with different ivars' do
+      array = [
+        Arel::Nodes::Over.new('foo', 'bar'),
+        Arel::Nodes::Over.new('foo', 'baz')
+      ]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/select_core_test.rb b/activerecord/test/cases/arel/nodes/select_core_test.rb
new file mode 100644
index 0000000000..bbb06666b6
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/select_core_test.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    class TestSelectCore < Arel::Test
+      def test_clone
+        core = Arel::Nodes::SelectCore.new
+        core.froms       = %w[a b c]
+        core.projections = %w[d e f]
+        core.wheres      = %w[g h i]
+
+        dolly = core.clone
+
+        assert_equal core.froms, dolly.froms
+        assert_equal core.projections, dolly.projections
+        assert_equal core.wheres, dolly.wheres
+
+        refute_same core.froms, dolly.froms
+        refute_same core.projections, dolly.projections
+        refute_same core.wheres, dolly.wheres
+      end
+
+      def test_set_quantifier
+        core = Arel::Nodes::SelectCore.new
+        core.set_quantifier = Arel::Nodes::Distinct.new
+        viz = Arel::Visitors::ToSql.new Table.engine.connection_pool
+        assert_match 'DISTINCT', viz.accept(core, Collectors::SQLString.new).value
+      end
+
+      def test_equality_with_same_ivars
+        core1 = SelectCore.new
+        core1.froms       = %w[a b c]
+        core1.projections = %w[d e f]
+        core1.wheres      = %w[g h i]
+        core1.groups      = %w[j k l]
+        core1.windows     = %w[m n o]
+        core1.havings     = %w[p q r]
+        core2 = SelectCore.new
+        core2.froms       = %w[a b c]
+        core2.projections = %w[d e f]
+        core2.wheres      = %w[g h i]
+        core2.groups      = %w[j k l]
+        core2.windows     = %w[m n o]
+        core2.havings     = %w[p q r]
+        array = [core1, core2]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        core1 = SelectCore.new
+        core1.froms       = %w[a b c]
+        core1.projections = %w[d e f]
+        core1.wheres      = %w[g h i]
+        core1.groups      = %w[j k l]
+        core1.windows     = %w[m n o]
+        core1.havings     = %w[p q r]
+        core2 = SelectCore.new
+        core2.froms       = %w[a b c]
+        core2.projections = %w[d e f]
+        core2.wheres      = %w[g h i]
+        core2.groups      = %w[j k l]
+        core2.windows     = %w[m n o]
+        core2.havings     = %w[l o l]
+        array = [core1, core2]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/select_statement_test.rb b/activerecord/test/cases/arel/nodes/select_statement_test.rb
new file mode 100644
index 0000000000..5e313e03fa
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/select_statement_test.rb
@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+describe Arel::Nodes::SelectStatement do
+  describe "#clone" do
+    it "clones cores" do
+      statement = Arel::Nodes::SelectStatement.new %w[a b c]
+
+      dolly = statement.clone
+      dolly.cores.must_equal      statement.cores
+      dolly.cores.wont_be_same_as statement.cores
+    end
+  end
+
+  describe 'equality' do
+    it 'is equal with equal ivars' do
+      statement1 = Arel::Nodes::SelectStatement.new %w[a b c]
+      statement1.offset = 1
+      statement1.limit  = 2
+      statement1.lock   = false
+      statement1.orders = %w[x y z]
+      statement1.with   = 'zomg'
+      statement2 = Arel::Nodes::SelectStatement.new %w[a b c]
+      statement2.offset = 1
+      statement2.limit  = 2
+      statement2.lock   = false
+      statement2.orders = %w[x y z]
+      statement2.with   = 'zomg'
+      array = [statement1, statement2]
+      assert_equal 1, array.uniq.size
+    end
+
+    it 'is not equal with different ivars' do
+      statement1 = Arel::Nodes::SelectStatement.new %w[a b c]
+      statement1.offset = 1
+      statement1.limit  = 2
+      statement1.lock   = false
+      statement1.orders = %w[x y z]
+      statement1.with   = 'zomg'
+      statement2 = Arel::Nodes::SelectStatement.new %w[a b c]
+      statement2.offset = 1
+      statement2.limit  = 2
+      statement2.lock   = false
+      statement2.orders = %w[x y z]
+      statement2.with   = 'wth'
+      array = [statement1, statement2]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/sql_literal_test.rb b/activerecord/test/cases/arel/nodes/sql_literal_test.rb
new file mode 100644
index 0000000000..0c4f23be78
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/sql_literal_test.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+require_relative '../helper'
+require 'yaml'
+
+module Arel
+  module Nodes
+    class SqlLiteralTest < Arel::Spec
+      before do
+        @visitor = Visitors::ToSql.new Table.engine.connection
+      end
+
+      def compile node
+        @visitor.accept(node, Collectors::SQLString.new).value
+      end
+
+      describe 'sql' do
+        it 'makes a sql literal node' do
+          sql = Arel.sql 'foo'
+          sql.must_be_kind_of Arel::Nodes::SqlLiteral
+        end
+      end
+
+      describe 'count' do
+        it 'makes a count node' do
+          node = SqlLiteral.new('*').count
+          compile(node).must_be_like %{ COUNT(*) }
+        end
+
+        it 'makes a distinct node' do
+          node = SqlLiteral.new('*').count true
+          compile(node).must_be_like %{ COUNT(DISTINCT *) }
+        end
+      end
+
+      describe 'equality' do
+        it 'makes an equality node' do
+          node = SqlLiteral.new('foo').eq(1)
+          compile(node).must_be_like %{ foo = 1 }
+        end
+
+        it 'is equal with equal contents' do
+          array = [SqlLiteral.new('foo'), SqlLiteral.new('foo')]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with different contents' do
+          array = [SqlLiteral.new('foo'), SqlLiteral.new('bar')]
+          assert_equal 2, array.uniq.size
+        end
+      end
+
+      describe 'grouped "or" equality' do
+        it 'makes a grouping node with an or node' do
+          node = SqlLiteral.new('foo').eq_any([1,2])
+          compile(node).must_be_like %{ (foo = 1 OR foo = 2) }
+        end
+      end
+
+      describe 'grouped "and" equality' do
+        it 'makes a grouping node with an and node' do
+          node = SqlLiteral.new('foo').eq_all([1,2])
+          compile(node).must_be_like %{ (foo = 1 AND foo = 2) }
+        end
+      end
+
+      describe 'serialization' do
+        it 'serializes into YAML' do
+          yaml_literal = SqlLiteral.new('foo').to_yaml
+          assert_equal('foo', YAML.load(yaml_literal))
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/sum_test.rb b/activerecord/test/cases/arel/nodes/sum_test.rb
new file mode 100644
index 0000000000..46c908d872
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/sum_test.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+class Arel::Nodes::SumTest < Arel::Spec
+  describe "as" do
+    it 'should alias the sum' do
+      table = Arel::Table.new :users
+      table[:id].sum.as('foo').to_sql.must_be_like %{
+        SUM("users"."id") AS foo
+      }
+    end
+  end
+
+  describe 'equality' do
+    it 'is equal with equal ivars' do
+      array = [Arel::Nodes::Sum.new('foo'), Arel::Nodes::Sum.new('foo')]
+      assert_equal 1, array.uniq.size
+    end
+
+    it 'is not equal with different ivars' do
+      array = [Arel::Nodes::Sum.new('foo'), Arel::Nodes::Sum.new('foo!')]
+      assert_equal 2, array.uniq.size
+    end
+  end
+  
+  describe 'order' do
+    it 'should order the sum' do
+      table = Arel::Table.new :users
+      table[:id].sum.desc.to_sql.must_be_like %{
+        SUM("users"."id") DESC
+      }
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/table_alias_test.rb b/activerecord/test/cases/arel/nodes/table_alias_test.rb
new file mode 100644
index 0000000000..b1b49919d5
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/table_alias_test.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'table alias' do
+      describe 'equality' do
+        it 'is equal with equal ivars' do
+          relation1 = Table.new(:users)
+          node1     = TableAlias.new relation1, :foo
+          relation2 = Table.new(:users)
+          node2     = TableAlias.new relation2, :foo
+          array = [node1, node2]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with different ivars' do
+          relation1 = Table.new(:users)
+          node1     = TableAlias.new relation1, :foo
+          relation2 = Table.new(:users)
+          node2     = TableAlias.new relation2, :bar
+          array = [node1, node2]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/true_test.rb b/activerecord/test/cases/arel/nodes/true_test.rb
new file mode 100644
index 0000000000..198e7b1aa4
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/true_test.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'True' do
+      describe 'equality' do
+        it 'is equal to other true nodes' do
+          array = [True.new, True.new]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with other nodes' do
+          array = [True.new, Node.new]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end
+
+
diff --git a/activerecord/test/cases/arel/nodes/unary_operation_test.rb b/activerecord/test/cases/arel/nodes/unary_operation_test.rb
new file mode 100644
index 0000000000..e76b59c8e1
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/unary_operation_test.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    class TestUnaryOperation < Arel::Test
+      def test_construct
+        operation = UnaryOperation.new :-, 1
+        assert_equal :-, operation.operator
+        assert_equal 1, operation.expr
+      end
+
+      def test_operation_alias
+        operation = UnaryOperation.new :-, 1
+        aliaz = operation.as('zomg')
+        assert_kind_of As, aliaz
+        assert_equal operation, aliaz.left
+        assert_equal 'zomg', aliaz.right
+      end
+
+      def test_operation_ordering
+        operation = UnaryOperation.new :-, 1
+        ordering = operation.desc
+        assert_kind_of Descending, ordering
+        assert_equal operation, ordering.expr
+        assert ordering.descending?
+      end
+
+      def test_equality_with_same_ivars
+        array = [UnaryOperation.new(:-, 1), UnaryOperation.new(:-, 1)]
+        assert_equal 1, array.uniq.size
+      end
+
+      def test_inequality_with_different_ivars
+        array = [UnaryOperation.new(:-, 1), UnaryOperation.new(:-, 2)]
+        assert_equal 2, array.uniq.size
+      end
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/update_statement_test.rb b/activerecord/test/cases/arel/nodes/update_statement_test.rb
new file mode 100644
index 0000000000..3a635f75d6
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/update_statement_test.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+describe Arel::Nodes::UpdateStatement do
+  describe "#clone" do
+    it "clones wheres and values" do
+      statement = Arel::Nodes::UpdateStatement.new
+      statement.wheres = %w[a b c]
+      statement.values = %w[x y z]
+
+      dolly = statement.clone
+      dolly.wheres.must_equal statement.wheres
+      dolly.wheres.wont_be_same_as statement.wheres
+
+      dolly.values.must_equal statement.values
+      dolly.values.wont_be_same_as statement.values
+    end
+  end
+
+  describe 'equality' do
+    it 'is equal with equal ivars' do
+      statement1 = Arel::Nodes::UpdateStatement.new
+      statement1.relation = 'zomg'
+      statement1.wheres   = 2
+      statement1.values   = false
+      statement1.orders   = %w[x y z]
+      statement1.limit    = 42
+      statement1.key      = 'zomg'
+      statement2 = Arel::Nodes::UpdateStatement.new
+      statement2.relation = 'zomg'
+      statement2.wheres   = 2
+      statement2.values   = false
+      statement2.orders   = %w[x y z]
+      statement2.limit    = 42
+      statement2.key      = 'zomg'
+      array = [statement1, statement2]
+      assert_equal 1, array.uniq.size
+    end
+
+    it 'is not equal with different ivars' do
+      statement1 = Arel::Nodes::UpdateStatement.new
+      statement1.relation = 'zomg'
+      statement1.wheres   = 2
+      statement1.values   = false
+      statement1.orders   = %w[x y z]
+      statement1.limit    = 42
+      statement1.key      = 'zomg'
+      statement2 = Arel::Nodes::UpdateStatement.new
+      statement2.relation = 'zomg'
+      statement2.wheres   = 2
+      statement2.values   = false
+      statement2.orders   = %w[x y z]
+      statement2.limit    = 42
+      statement2.key      = 'wth'
+      array = [statement1, statement2]
+      assert_equal 2, array.uniq.size
+    end
+  end
+end
diff --git a/activerecord/test/cases/arel/nodes/window_test.rb b/activerecord/test/cases/arel/nodes/window_test.rb
new file mode 100644
index 0000000000..81ecd5ced8
--- /dev/null
+++ b/activerecord/test/cases/arel/nodes/window_test.rb
@@ -0,0 +1,80 @@
+# frozen_string_literal: true
+require_relative '../helper'
+
+module Arel
+  module Nodes
+    describe 'Window' do
+      describe 'equality' do
+        it 'is equal with equal ivars' do
+          window1 = Window.new
+          window1.orders = [1, 2]
+          window1.partitions = [1]
+          window1.frame 3
+          window2 = Window.new
+          window2.orders = [1, 2]
+          window2.partitions = [1]
+          window2.frame 3
+          array = [window1, window2]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with different ivars' do
+          window1 = Window.new
+          window1.orders = [1, 2]
+          window1.partitions = [1]
+          window1.frame 3
+          window2 = Window.new
+          window2.orders = [1, 2]
+          window1.partitions = [1]
+          window2.frame 4
+          array = [window1, window2]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+
+    describe 'NamedWindow' do
+      describe 'equality' do
+        it 'is equal with equal ivars' do
+          window1 = NamedWindow.new 'foo'
+          window1.orders = [1, 2]
+          window1.partitions = [1]
+          window1.frame 3
+          window2 = NamedWindow.new 'foo'
+          window2.orders = [1, 2]
+          window2.partitions = [1]
+          window2.frame 3
+          array = [window1, window2]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with different ivars' do
+          window1 = NamedWindow.new 'foo'
+          window1.orders = [1, 2]
+          window1.partitions = [1]
+          window1.frame 3
+          window2 = NamedWindow.new 'bar'
+          window2.orders = [1, 2]
+          window2.partitions = [1]
+          window2.frame 3
+          array = [window1, window2]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+
+    describe 'CurrentRow' do
+      describe 'equality' do
+        it 'is equal to other current row nodes' do
+          array = [CurrentRow.new, CurrentRow.new]
+          assert_equal 1, array.uniq.size
+        end
+
+        it 'is not equal with other nodes' do
+          array = [CurrentRow.new, Node.new]
+          assert_equal 2, array.uniq.size
+        end
+      end
+    end
+  end
+end