Improve alias tests

test/t/class.rb

@@ -229,26 +229,3 @@ end
 assert('Class Dup 2') do
   module M; end;  M.dup.class == Module
 end
-
-assert('Class Alias 1') do
-  class A
-    def test; 1; end
-
-    alias test2 test
-    alias :test3 :test
-  end
-
-  A.new.test2 == 1 and A.new.test3 == 1
-end
-
-assert('Class Alias 2') do
-  class A
-    def test; 1; end
-
-    alias test2 test
-
-    def test; 2; end
-  end
-
-  A.new.test == 2 and A.new.test2 == 1
-end

test/t/methods.rb

 ##
-# Chapter 13 "Class and modules" ISO Test
+# Chapter 13.3 "Methods" ISO Test
+
+assert('The alias statement', '13.3.6 a) 4)') do
+  # check aliasing in all possible ways
+
+  def alias_test_method_original; true; end
+
+  alias alias_test_method_a alias_test_method_original
+  alias :alias_test_method_b :alias_test_method_original
+
+  assert_true(alias_test_method_original)
+  assert_true(alias_test_method_a)
+  assert_true(alias_test_method_b)
+end
+
+assert('The alias statement (overwrite original)', '13.3.6 a) 4)') do
+  # check that an aliased method can be overwritten
+  # without side effect
+
+  def alias_test_method_original; true; end
+
+  alias alias_test_method_a alias_test_method_original
+  alias :alias_test_method_b :alias_test_method_original
+
+  assert_true(alias_test_method_original)
+
+  def alias_test_method_original; false; end
+
+  assert_false(alias_test_method_original)
+  assert_true(alias_test_method_a)
+  assert_true(alias_test_method_b)
+end
+
+assert('The alias statement', '13.3.6 a) 5)') do
+  # check that alias is raising NameError if
+  # non-existing method should be undefined
+
+  assert_raise(NameError) do
+    alias new_name_a non_existing_method
+  end
+
+  assert_raise(NameError) do
+    alias :new_name_b :non_existing_method
+  end
+end
 
 assert('The undef statement', '13.3.7 a) 4)') do
   # check that undef is undefining method