diff --git a/activemodel/lib/active_model/type/boolean.rb b/activemodel/lib/active_model/type/boolean.rb
index bcdbab0343..f6c6efbc87 100644
--- a/activemodel/lib/active_model/type/boolean.rb
+++ b/activemodel/lib/active_model/type/boolean.rb
@@ -20,6 +20,10 @@ def type # :nodoc:
         :boolean
       end
 
+      def serialize(value) # :nodoc:
+        cast(value)
+      end
+
       private
 
         def cast_value(value)
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index fcfab074a2..d216fe16fa 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -14,7 +14,6 @@
 require "models/project"
 require "models/default"
 require "models/auto_id"
-require "models/boolean"
 require "models/column_name"
 require "models/subscriber"
 require "models/comment"
@@ -716,48 +715,6 @@ def test_attributes
     assert_equal expected_attributes, category.attributes
   end
 
-  def test_boolean
-    b_nil = Boolean.create("value" => nil)
-    nil_id = b_nil.id
-    b_false = Boolean.create("value" => false)
-    false_id = b_false.id
-    b_true = Boolean.create("value" => true)
-    true_id = b_true.id
-
-    b_nil = Boolean.find(nil_id)
-    assert_nil b_nil.value
-    b_false = Boolean.find(false_id)
-    assert_not_predicate b_false, :value?
-    b_true = Boolean.find(true_id)
-    assert_predicate b_true, :value?
-  end
-
-  def test_boolean_without_questionmark
-    b_true = Boolean.create("value" => true)
-    true_id = b_true.id
-
-    subclass   = Class.new(Boolean).find true_id
-    superclass = Boolean.find true_id
-
-    assert_equal superclass.read_attribute(:has_fun), subclass.read_attribute(:has_fun)
-  end
-
-  def test_boolean_cast_from_string
-    b_blank = Boolean.create("value" => "")
-    blank_id = b_blank.id
-    b_false = Boolean.create("value" => "0")
-    false_id = b_false.id
-    b_true = Boolean.create("value" => "1")
-    true_id = b_true.id
-
-    b_blank = Boolean.find(blank_id)
-    assert_nil b_blank.value
-    b_false = Boolean.find(false_id)
-    assert_not_predicate b_false, :value?
-    b_true = Boolean.find(true_id)
-    assert_predicate b_true, :value?
-  end
-
   def test_new_record_returns_boolean
     assert_equal false, Topic.new.persisted?
     assert_equal true, Topic.find(1).persisted?
diff --git a/activerecord/test/cases/boolean_test.rb b/activerecord/test/cases/boolean_test.rb
new file mode 100644
index 0000000000..ab9f974e2c
--- /dev/null
+++ b/activerecord/test/cases/boolean_test.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/boolean"
+
+class BooleanTest < ActiveRecord::TestCase
+  def test_boolean
+    b_nil   = Boolean.create!(value: nil)
+    b_false = Boolean.create!(value: false)
+    b_true  = Boolean.create!(value: true)
+
+    assert_nil Boolean.find(b_nil.id).value
+    assert_not_predicate Boolean.find(b_false.id), :value?
+    assert_predicate Boolean.find(b_true.id), :value?
+  end
+
+  def test_boolean_without_questionmark
+    b_true = Boolean.create!(value: true)
+
+    subclass   = Class.new(Boolean).find(b_true.id)
+    superclass = Boolean.find(b_true.id)
+
+    assert_equal superclass.read_attribute(:has_fun), subclass.read_attribute(:has_fun)
+  end
+
+  def test_boolean_cast_from_string
+    b_blank = Boolean.create!(value: "")
+    b_false = Boolean.create!(value: "0")
+    b_true  = Boolean.create!(value: "1")
+
+    assert_nil Boolean.find(b_blank.id).value
+    assert_not_predicate Boolean.find(b_false.id), :value?
+    assert_predicate Boolean.find(b_true.id), :value?
+  end
+
+  def test_find_by_boolean_string
+    b_false = Boolean.create!(value: "false")
+    b_true  = Boolean.create!(value: "true")
+
+    assert_equal b_false, Boolean.find_by(value: "false")
+    assert_equal b_true, Boolean.find_by(value: "true")
+  end
+end