Improved test_stub_callable_keyword_args to test pass-through.

[git-p4: depot-paths = "//src/minitest/dev/": change = 13022]

lib/minitest/mock.rb

@@ -207,7 +207,9 @@ class Object
   #         assert obj_under_test.stale?
   #       end
   #     end
-  #
+  #--
+  # NOTE: keyword args in callables are NOT checked for correctness
+  # against the existing method. Too many edge cases to be worth it.
 
   def stub name, val_or_callable, *block_args
     new_name = "__minitest_stub__#{name}"

test/minitest/test_minitest_mock.rb

@@ -598,8 +598,8 @@ class TestMinitestStub < Minitest::Test
   end
 
   def test_stub_callable_keyword_args
-    Keywords.stub :args, ->(*args, **kws) { 42 } do
-      @tc.assert_equal 42, Keywords.args("woot", kw1:314)
+    Keywords.stub :args, ->(*args, **kws) { [args, kws] } do
+      @tc.assert_equal [["woot"], { kw1: 42 }], Keywords.args("woot", kw1: 42)
     end
   end