Add assert_not_equal

test/assert.rb

@@ -105,6 +105,12 @@ def assert_equal(exp, act, msg = nil)
   assert_true(exp == act, msg, diff)
 end
 
+def assert_not_equal(exp, act, msg = nil)
+  msg = "Expected to be not equal" unless msg
+  diff = assertion_diff(exp, act)
+  assert_false(exp == act, msg, diff)
+end
+
 def assert_nil(obj, msg = nil)
   msg = "Expected #{obj.inspect} to be nil" unless msg
   diff = assertion_diff(nil, obj)