Add specs for Data#members

Author: andrykonchin

spec/ruby/core/data/fixtures/classes.rb

@@ -1,5 +1,7 @@
 module DataSpecs
   guard -> { ruby_version_is "3.2" and Data.respond_to?(:define) } do
     Measure = Data.define(:amount, :unit)
+
+    class DataSubclass < Data; end
   end
 end

spec/ruby/core/data/members_spec.rb

@@ -0,0 +1,23 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+ruby_version_is "3.2" do
+  describe "Data#members" do
+    it "returns an array of attribute names" do
+      measure = DataSpecs::Measure.new(amount: 42, unit: 'km')
+      measure.members.should == [:amount, :unit]
+    end
+  end
+
+  describe "DataClass#members" do
+    it "returns an array of attribute names" do
+      DataSpecs::Measure.members.should == [:amount, :unit]
+    end
+
+    context "class inheriting Data" do
+      it "isn't available in a subclass" do
+        DataSpecs::DataSubclass.should_not.respond_to?(:members)
+      end
+    end
+  end
+end