1 files changed, 101 insertions, 0 deletions
diff --git a/activesupport/test/core_ext/class/attribute_test.rb b/activesupport/test/core_ext/class/attribute_test.rb
new file mode 100644
index 0000000000..be6ad82367
--- /dev/null
+++ b/activesupport/test/core_ext/class/attribute_test.rb
@@ -0,0 +1,101 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+require "active_support/core_ext/class/attribute"
+
+class ClassAttributeTest < ActiveSupport::TestCase
+  def setup
+    @klass = Class.new do
+      class_attribute :setting
+      class_attribute :timeout, default: 5
+    end
+
+    @sub = Class.new(@klass)
+  end
+
+  test "defaults to nil" do
+    assert_nil @klass.setting
+    assert_nil @sub.setting
+  end
+
+  test "custom default" do
+    assert_equal 5, @klass.timeout
+  end
+
+  test "inheritable" do
+    @klass.setting = 1
+    assert_equal 1, @sub.setting
+  end
+
+  test "overridable" do
+    @sub.setting = 1
+    assert_nil @klass.setting
+
+    @klass.setting = 2
+    assert_equal 1, @sub.setting
+
+    assert_equal 1, Class.new(@sub).setting
+  end
+
+  test "predicate method" do
+    assert_equal false, @klass.setting?
+    @klass.setting = 1
+    assert_equal true, @klass.setting?
+  end
+
+  test "instance reader delegates to class" do
+    assert_nil @klass.new.setting
+
+    @klass.setting = 1
+    assert_equal 1, @klass.new.setting
+  end
+
+  test "instance override" do
+    object = @klass.new
+    object.setting = 1
+    assert_nil @klass.setting
+    @klass.setting = 2
+    assert_equal 1, object.setting
+  end
+
+  test "instance predicate" do
+    object = @klass.new
+    assert_equal false, object.setting?
+    object.setting = 1
+    assert_equal true, object.setting?
+  end
+
+  test "disabling instance writer" do
+    object = Class.new { class_attribute :setting, instance_writer: false }.new
+    assert_raise(NoMethodError) { object.setting = "boom" }
+  end
+
+  test "disabling instance reader" do
+    object = Class.new { class_attribute :setting, instance_reader: false }.new
+    assert_raise(NoMethodError) { object.setting }
+    assert_raise(NoMethodError) { object.setting? }
+  end
+
+  test "disabling both instance writer and reader" do
+    object = Class.new { class_attribute :setting, instance_accessor: false }.new
+    assert_raise(NoMethodError) { object.setting }
+    assert_raise(NoMethodError) { object.setting? }
+    assert_raise(NoMethodError) { object.setting = "boom" }
+  end
+
+  test "disabling instance predicate" do
+    object = Class.new { class_attribute :setting, instance_predicate: false }.new
+    assert_raise(NoMethodError) { object.setting? }
+  end
+
+  test "works well with singleton classes" do
+    object = @klass.new
+    object.singleton_class.setting = "foo"
+    assert_equal "foo", object.setting
+  end
+
+  test "setter returns set value" do
+    val = @klass.send(:setting=, 1)
+    assert_equal 1, val
+  end
+end