Test all ISO defined classes direct superclass except `Object` class.

Move mrbgems ISO direct superclass test to `superclass.rb`.
Skips test if class isn't defined.
Close #2332.

mrbgems/mruby-struct/test/struct.rb

@@ -5,10 +5,6 @@ assert('Struct', '15.2.18') do
   Struct.class == Class
 end
 
-assert('Struct superclass', '15.2.18.2') do
-  Struct.superclass == Object
-end
-
 assert('Struct.new', '15.2.18.3.1') do
   c = Struct.new(:m1, :m2)
   c.superclass == Struct and

mrbgems/mruby-time/test/time.rb

@@ -9,10 +9,6 @@ assert('Time', '15.2.19') do
   Time.class == Class
 end
 
-assert('Time superclass', '15.2.19.2') do
-  Time.superclass == Object
-end
-
 assert('Time.at', '15.2.19.6.1') do
   Time.at(1300000000.0)
 end

test/t/superclass.rb

 [
+  # [:Object, :implementation_defined_value, '15.2.2.1'],
   [:Module, :Object, '15.2.2.2'],
   [:Class, :Module, '15.2.3.2'],
   [:NilClass, :Object, '15.2.4.2'],
@@ -12,19 +13,34 @@
   [:Array, :Object, '15.2.12.2'],
   [:Hash, :Object, '15.2.13.2'],
   [:Range, :Object, '15.2.14.2'],
+  [:Regexp, :Object, '15.2.15.2'],
+  [:MatchData, :Object, '15.2.16.2'],
   [:Proc, :Object, '15.2.17.2'],
+  [:Struct, :Object, '15.2.18.2'],
+  [:Time, :Object, '15.2.19.2'],
+  [:IO, :Object, '15.2.20.2'],
+  [:File, :IO, '15.2.21.2'],
   [:Exception, :Object, '15.2.22.2'],
   [:StandardError, :Exception, '15.2.23.2'],
   [:ArgumentError, :StandardError, '15.2.24.2'],
+  [:LocalJumpError, :StandardError, '15.2.25.2'],
   [:RangeError, :StandardError, '12.2.26.2'],
+  [:RegexpError, :StandardError, '12.2.27.2'],
+  [:RuntimeError, :StandardError, '12.2.28.2'],
   [:TypeError, :StandardError, '12.2.29.2'],
+  [:ZeroDivisionError, :StandardError, '12.2.30.2'],
   [:NameError, :StandardError, '15.2.31.2'],
   [:NoMethodError, :NameError, '15.2.32.2'],
   [:IndexError, :StandardError, '15.2.33.2'],
+  [:IOError, :StandardError, '12.2.34.2'],
+  [:EOFError, :IOError, '12.2.35.2'],
+  [:SystemCallError, :StandardError, '15.2.36.2'],
+  [:ScriptError, :Exception, '12.2.37.2'],
+  [:SyntaxError, :ScriptError, '12.2.38.2'],
+  [:LoadError, :ScriptError, '12.2.39,2'],
 ].each do |cls, super_cls, iso|
   assert "Direct superclass of #{cls}", iso do
-    assert_true Object.const_defined? cls
-    assert_true Object.const_defined? super_cls
+    skip "#{cls} isn't defined" unless Object.const_defined? cls
     assert_equal Object.const_get(super_cls), Object.const_get(cls).superclass
   end
 end