diff --git a/rust/src/rbs/method_loader.rb b/rust/src/rbs/method_loader.rb
index 2694c0c..a0f8f05 100644
--- a/rust/src/rbs/method_loader.rb
+++ b/rust/src/rbs/method_loader.rb
@@ -12,6 +12,7 @@ class MethodLoader
       String Integer Float Array Hash Symbol
       TrueClass FalseClass NilClass
       Range Regexp Struct Enumerable
+      Kernel Object
     ].freeze
 
     def initialize
diff --git a/test/kernel_test.rb b/test/kernel_test.rb
new file mode 100644
index 0000000..d57f221
--- /dev/null
+++ b/test/kernel_test.rb
@@ -0,0 +1,178 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class KernelTest < Minitest::Test
+  include CLITestHelper
+
+  # ============================================
+  # No Error
+  # ============================================
+
+  def test_freeze_on_integer
+    source = <<~RUBY
+      class Freezer
+        def freeze_value
+          x = 42
+          x.freeze
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_frozen_on_string
+    source = <<~RUBY
+      class Checker
+        def check
+          x = "hello"
+          x.frozen?
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_tap_on_string
+    source = <<~RUBY
+      class Logger
+        def log
+          x = "hello"
+          x.tap
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_object_id_on_string
+    source = <<~RUBY
+      class Inspector
+        def inspect_id
+          x = "hello"
+          x.object_id
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_send_on_string
+    source = <<~RUBY
+      class Caller
+        def dynamic_call
+          x = "hello"
+          x.send(:upcase)
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_kernel_methods_on_array
+    source = <<~RUBY
+      class Processor
+        def process
+          x = [1, 2, 3]
+          x.freeze
+          x.frozen?
+          x.object_id
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_kernel_methods_on_hash
+    source = <<~RUBY
+      class Processor
+        def process
+          x = { a: 1 }
+          x.freeze
+          x.frozen?
+          x.object_id
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  # ============================================
+  # Override
+  # ============================================
+
+  def test_override_freeze_no_error
+    source = <<~RUBY
+      class Foo
+        def freeze
+          self
+        end
+
+        def bar
+          freeze
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_override_hash_no_error
+    source = <<~RUBY
+      class Foo
+        def hash
+          42
+        end
+
+        def bar
+          hash.even?
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  # ============================================
+  # Error Detection (Override)
+  # ============================================
+
+  def test_override_freeze_return_type_error
+    source = <<~RUBY
+      class Foo
+        def freeze
+          self
+        end
+
+        def bar
+          freeze.baz
+        end
+      end
+    RUBY
+
+    assert_check_error(source, method_name: 'baz', receiver_type: 'Foo')
+  end
+
+  def test_override_hash_return_type_error
+    source = <<~RUBY
+      class Foo
+        def hash
+          42
+        end
+
+        def bar
+          hash.upcase
+        end
+      end
+    RUBY
+
+    assert_check_error(source, method_name: 'upcase', receiver_type: 'Integer')
+  end
+end
diff --git a/test/method_loader_test.rb b/test/method_loader_test.rb
new file mode 100644
index 0000000..212f2c3
--- /dev/null
+++ b/test/method_loader_test.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class MethodLoaderTest < Minitest::Test
+  def setup
+    require_relative '../rust/src/rbs/method_loader'
+    @loader = Rbs::MethodLoader.new
+    @results = @loader.load_methods
+  end
+
+  def test_existing_classes_still_loaded
+    loaded_classes = @results.map { |r| r[:receiver_class] }.uniq
+    %w[String Integer Float Array Hash Symbol Kernel Object].each do |cls|
+      assert_includes loaded_classes, cls, "#{cls} should be loaded"
+    end
+  end
+end
diff --git a/test/object_test.rb b/test/object_test.rb
new file mode 100644
index 0000000..a93c9f0
--- /dev/null
+++ b/test/object_test.rb
@@ -0,0 +1,241 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class ObjectTest < Minitest::Test
+  include CLITestHelper
+
+  # ============================================
+  # No Error
+  # ============================================
+
+  def test_nil_check_on_string
+    source = <<~RUBY
+      class Checker
+        def check
+          x = "hello"
+          x.nil?
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_nil_check_on_integer
+    source = <<~RUBY
+      class Checker
+        def check
+          x = 42
+          x.nil?
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_class_method_on_string
+    source = <<~RUBY
+      class Inspector
+        def inspect_type
+          x = "hello"
+          x.class
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_dup_on_string
+    source = <<~RUBY
+      class Copier
+        def copy
+          x = "hello"
+          x.dup
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_freeze_on_string
+    source = <<~RUBY
+      class Freezer
+        def freeze_value
+          x = "hello"
+          x.freeze
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_frozen_check_on_array
+    source = <<~RUBY
+      class Checker
+        def check
+          x = [1, 2, 3]
+          x.frozen?
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_is_a_on_string
+    source = <<~RUBY
+      class TypeChecker
+        def check
+          x = "hello"
+          x.is_a?(String)
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_respond_to_on_integer
+    source = <<~RUBY
+      class Checker
+        def check
+          x = 42
+          x.respond_to?(:even?)
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_to_s_on_integer
+    source = <<~RUBY
+      class Converter
+        def convert
+          x = 42
+          x.to_s
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_hash_method_on_string
+    source = <<~RUBY
+      class Hasher
+        def compute
+          x = "hello"
+          x.hash
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_equal_check_on_integer
+    source = <<~RUBY
+      class Comparer
+        def compare
+          x = 42
+          x.equal?(42)
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_object_methods_on_hash
+    source = <<~RUBY
+      class Processor
+        def process
+          x = { a: 1 }
+          x.nil?
+          x.frozen?
+          x.class
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  # ============================================
+  # Override
+  # ============================================
+
+  def test_override_to_s_no_error
+    source = <<~RUBY
+      class Foo
+        def to_s
+          "Foo"
+        end
+
+        def bar
+          to_s.upcase
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  def test_override_nil_no_error
+    source = <<~RUBY
+      class Foo
+        def nil?
+          false
+        end
+
+        def bar
+          nil?
+        end
+      end
+    RUBY
+
+    assert_no_check_errors(source)
+  end
+
+  # ============================================
+  # Error Detection (Override)
+  # ============================================
+
+  def test_override_to_s_return_type_error
+    source = <<~RUBY
+      class Foo
+        def to_s
+          "Foo"
+        end
+
+        def bar
+          to_s.even?
+        end
+      end
+    RUBY
+
+    assert_check_error(source, method_name: 'even?', receiver_type: 'String')
+  end
+
+  def test_override_dup_return_type_error
+    source = <<~RUBY
+      class Foo
+        def dup
+          "copy"
+        end
+
+        def bar
+          dup.even?
+        end
+      end
+    RUBY
+
+    assert_check_error(source, method_name: 'even?', receiver_type: 'String')
+  end
+end