[Cppunit-devel] Some interesting ideas I am looking at

[King D. <Ki...@tc...>]

First, I recently discovered the idea of MockObjects (www.mockobjects.com)
which is sort of a framework for creating stub-like objects (mock objects
are not the same as a stub) upon which you can set expectations and they
will verify themself. For instance you could create a mock ostream object
and tell it what you expect to be written to it and if something else is
written then it will fail. Before discovering the idea, I already did
something like this, but it was all hand written as opposed to using a
ready-made framework.  There are mockobjects for Java that work with Junit,
but none for C++ so I started some work on creating a C++ equivalent.

However, just as with cppunit things would be a whole lot nicer if C++ had
reflection like Java does. While doing some research, I stumbled across
something called OpenC++
(http://www.csg.is.titech.ac.jp/~chiba/openc++.html). It is kind of hard to
explain what exactly OpenC++ is (the documentation does a very lousy job),
but it is sort of translating preprocessor for C++ that lets you add your
own language extensions. It reads in your source files and various meta
classes that you write and spits out C++ code. You have full access to the
parse tree of the source code and can modify it and do reflection. You could
think of it as a much smarter version of the preprocessor, but that would
hardly be doing it justice.

I know my explanation does not do it justice, but consider an example
related to CppUnit. Instead of all the mucking about with preprocessor
macros and templates like CPPUNIT_TEST_SUITE stuff, you could actually
define a language extension using for example class and method modifiers
(testsuite and testcase in the example):

class testsuite FooBarTests
{
public:
    testcase void testFoo();
    testcase void testBar();
};

And this could generate the suite method adding all test cases to it,
getting their names from their declarations. An alternative syntax idea
could be to use a user defined access modifier

class testsuite FooBarTests
{
public:
testcases:
    void testFoo();
    void testBar();
};

Or the testsuite metaclass could do like junit and simply add all methods
with a signature of void testXXX() as test cases. There are many
possibilities.

This would also be helpful in something that is a big problem right now with
CppUnit, how to use decorators with the macros. Currently you can't and
there isn't a good solution particularly with the notion that decorated
tests have a variable number of parameters. But imagine doing:

class testsuite FooBarTests
{
public:
    testcase decorator( RepeatedTest, 5 ) void testFoo();
    testcase void testBar();
};

This would decorate the testFoo case, by wrapping it with a RepeatedTest
test decorator with a parameter of 5. (Of course test decorators need to get
their test ownership issues fixed).

It would be a lot cleaner, and avoid duplication of names as macro
parameters.

This would be helpful with MockObjects, because in the Java version you can
create a mock object and it uses reflection to just examine the class of the
object and iterate through all fields looking for ones that implement the
Expectation interface and calls their verify method. All it took to add an
expectation was to add the field to the class. Of course in straight C++ it
is not so simple. I could try to do something like what CppUnit does with
the CPPUNIT_TEST_SUITE stuff which requires declaring things twice. But I
think a better idea is to use OpenC++ and extend the language to add
mockobjects that would generate code that called verify on all members that
implement the Expectation interface.

I just thought I would solicit any thoughts on the subject from the group.
Note, I am going on vacation tomorrow so it will be a week or so before I
get back with anyone.