Test deprecation warning with $;

test/ruby/test_exception.rb

@@ -1111,19 +1111,13 @@ def test_warning_warn
   end
 
   def test_warn_deprecated_backwards_compatibility_category
-    omit "no method to test"
-
-    warning = capture_warning_warn { }
-
-    assert_match(/deprecated/, warning[0])
-  end
-
-  def test_warn_deprecated_category
-    omit "no method to test"
-
-    warning = capture_warning_warn(category: true) { }
+    (message, category), = capture_warning_warn(category: true) do
+      $; = "www"
+      $; = nil
+    end
 
-    assert_equal :deprecated, warning[0][1]
+    assert_include message, 'deprecated'
+    assert_equal :deprecated, category
   end
 
   def test_kernel_warn_uplevel